What Can We Expect Robbie Erlin To Do?


We’re ten years past Moneyball, and there is still a lot of hesitancy about endorsing so-called “performance prospects”–players whose prospect status is built more on production than tools and projection. Sometimes (Yusmeiro Petit) this skepticism proves justified, while other times (Doug Fister), it looks like a major oversight in retrospect.

When I see somebody project one of these players as a “second-division starter” or “back-of-the-rotation guy,” or some other somewhat pessimistic endorsement, I like to ask what exactly they project to happen on a statistical level when the player reaches the major leagues. Petit, for example, was undone by the home run ball in the majors, and his strikeout rate plummeted. Fister was successful because he was able to translate his very low walk rates, allowing him to pitch very well in spite of average strikeout and groundball numbers.

Depending on how one defines “performance prospect,” there may be no better one in baseball right now than Robbie Erlin of San Diego, who had a 154/16 K/BB ratio in 147 1/3 innings between High-A and Double-A at age 21 in 2011. Among the 378 pitchers with 120+ innings, he ranked third in walk rate (2.8%, just .1% off the lead), 19th in strikeout rate (26.8%), second in strikeout-to-walk ratio (9.63), and tied for third in WHIP (0.95).

Most project Erlin as a #3/#4-type starter. It thus goes without saying that these skeptics project something to decline statistically from Double-A to the majors for him. What exactly might that be, and what shape is Erlin’s MLB performance likely to take? Let’s take an empirical look at this.

We may not know what Erlin’s performance will look like, but we can get a pretty good idea of what pitches he’ll be throwing. Most scouting reports list Erlin as working somewhere in the 87-93 range with his fastball as well as throwing a curveball and changeup. The Brooks Baseball Pitch F/X readouts from two of his outings this spring (here and here) seem to back that up, listing him as throwing a fastball in the 88-92 range, a curveball around 71-74, and some other stuff (the changeup, though it’s misclassified there) in the 78-82 range. Now, there are some issues with taking these spring outings as gospel–for one, he’s still rounding into shape in March, and for another, these outings aren’t as long as a typical start would be–but this seems to line up with most reports on him, so it’s a fair place to start.

What else might we be able to say about Erlin? I think even his most staunch detractors would have to admit that he’s likely to throw a lot of strikes in the majors. It would be a surprise to see him have a walk rate higher than 2.5 BB/9, I would think.

On the flip side, Erlin is an extreme flyball pitcher, with a 35.1% groundball rate last year per Minor League Central. I think it’s a strong bet that he’s unlikely to get that over 40% in the majors without some major adjustments–adjustments he may not care to make, especially with San Diego as his home park.

With this established, I decided to comb through the last ten years of MLB data to unearth pitcher seasons that met the following criteria.

–30+ IP as a starter
–Average fastball velocity between 88 mph and 90.5 mph
–Average curveball velocity below 74 mph
–Changeup velocity between 78 mph and 82 mph
–Walk rate below 2.5 BB/9
–Groundball rate below 40%

There are 16 such seasons. I wish I could’ve been even more specific in my criteria, but doing so would’ve narrowed the pool to basically zero.

What I’m going to do here is take a look at what sort of strikeout rate and FIP these pitchers produced in these 16 seasons. That’s the aspect of Erlin’s performance that’s harder to predict–how well he’ll miss bats at the big league level, and what the sum total of his performance will be. So let’s see what we get here.

The Great

Pedro Martinez, 2005, 88.0 mph fastball, 72.8 mph curve, 78.2 mph changeup, 1.95 BB/9, 37.9% GB, 8.63 K/9, 2.95 FIP
Jered Weaver, 2010, 89.9 mph fastball, 70.7 mph curve, 78.6 mph changeup, 2.17 BB/9, 36.0% GB, 9.35 K/9, 3.06 FIP
Jered Weaver, 2011, 89.1 mph fastball, 71.6 mph curve, 78.9 mph changeup, 2.14 BB/9, 32.5% GB, 7.56 K/9, 3.20 FIP

Interesting stuff, here. It’s a fairly well-kept secret that Jered Weaver doesn’t throw all that hard, and that Pedro’s velocity plummeted before his effectiveness did. It’s interesting that Pedro turned in the best FIP of all 16 seasons despite the lowest velocity–speed isn’t everything, kids!

Obviously, there are a number of reasons to believe Erlin won’t reach this level. His changeup is good, but it’s not the nastiest offspeed pitch in the history of the game. Pedro was also a veteran pitcher who had obviously figured out how to retire hitters at absurd clips long before this season (which leads to an interesting question for another column–is there such a thing as “old player skills” for pitchers?).

As for Weaver, obviously his mechanics are one of a kind, though it is worth noting Erlin does have a hip turn in his delivery, though nowhere near as exaggerated as Weaver’s is. At 6’7″, Weaver can also work angles to the plate much more effectively than the 6’0″ Erlin can, and he also has a fourth pitch–a slider–that’s a big part of his arsenal.

The Not-So-Great

Eric Milton, 2006, 88.1 mph fastball, 72.4 mph curve, 78.2 mph changeup, 2.48 BB/9, 30.8% GB, 5.31 K/9, 5.36 FIP
Zack Greinke, 2004, 89.1 mph fastball, 70.6 mph curve, 78.6 mph changeup, 1.61 BB/9, 34.6% GB, 6.21 K/9, 4.70 FIP
Bronson Arroyo, 2005, 89.5 mph fastball, 72.5 mph curve, 79.7 mph changeup, 2.37 BB/9, 37.9% GB,  4.38 K/9, 4.43 FIP
Jon Garland, 2007, 89.3 mph fastball, 73.4 mph curve, 78.5 mph changeup, 2.46 BB/9, 39.4% GB, 4.23 K/9, 4.36 FIP

Milton’s 2006 is the only truly awful season of the 16, which in itself is telling–it’s tough to not be worthy of an MLB rotation spot if you can throw a lot of strikes with even fringe-average stuff. Greinke’s season is really odd–for one, nobody thinks of Zack Greinke and remembers he had a season where he averaged under 90 mph with his fastball, and for another, he never approached a 1.61 BB/9 again. This was his age-20 rookie season–he would later evolve into a 92-94 mph power pitcher with less prohibitive groundball rates but more walks.

This was Arroyo’s final year with the Red Sox, and he would never have a strikeout rate this bad again, though interestingly, he never threw harder than he did in 2005 (Again, velocity isn’t everything!). This was also Garland’s last year with the White Sox, and the only year the groundball hurler had a GB% below 40–oddly, it’s also the year he posted his best HR/9, hence the reasonable FIP despite a poor K/BB ratio (4.79 xFIP). He also hasn’t had a BB/9 below 2.50 since.

I have to think Erlin can do better than this. The guy has better stuff than late-career Eric Milton, and his offspeed stuff is miles ahead of Garland’s pedestrian collection of offerings. Arroyo’s season seems to be an anomaly even for him (which I’ll get to in a minute), and I’d think it quite unreasonable to project Erlin for such a Livan Hernandez-esque strikeout rate given the movement of his offspeed offerings. Greinke’s season is just so odd that I’m not even sure what to say about it in relation to Erlin. Honestly, if he can post 3.85 K/BB ratios like Greinke did in that season, he’ll have done his job–Greinke’s FIP was inflated by a 12.8% HR/FB ratio, so it really wasn’t that bad a year.

The Middle Ground

Travis Wood, 2010, 89.9 mph fastball, 72.9 mph curve, 78.6 mph changeup, 2.28 BB/9, 30.5% GB, 7.54 K/9, 3.42 FIP
Glendon Rusch, 2004, 88.2 mph fastball, 72.8 mph curve, 79.8 mph changeup, 2.29 BB/9, 39.8 % GB, 6.25 K/9, 3.52 FIP
Javier Vazquez, 2011, 90.4 mph fastball, 73.3 mph curve, 79.6 mph changeup, 2.34 BB/9, 34.2% GB, 7.57 K/9, 3.57 FIP
Cliff Lee, 2005, 89.3 mph fastball, 73.8 mph curve, 82.0 mph changeup, 2.32 BB/9, 35.6% GB, 6.37 K/9, 3.79 FIP
Orlando Hernandez, 2002, 88.8 mph fastball, 74.0 mph curve, 80.6 mph changeup, 2.22 BB/9, 37.0% GB, 6.97 K/9, 3.83 FIP
Randy Wolf, 2009, 89.0 mph fastball, 67.2 mph curve, 78.5 mph changeup, 2.44 BB/9, 39.6% GB, 6.72 K/9, 3.96 FIP
Bronson Arroyo, 2006, 89.0 mph fastball,71.3 mph curve, 78.2 mph changeup, 2.39 BB/9, 38.2% GB, 6.88 K/9, 4.15 FIP
Ted Lilly, 2007, 88.4 mph fastball, 70.7 mph curve, 79.3 mph changeup, 2.39 BB/9, 33.7% GB, 7.57 K/9, 4.16 FIP
Curt Schilling, 2007, 89.0 mph fastball, 72.7 mph curve, 80.8 mph changeup, 1.37 BB/9, 37.3% GB, 6.02 K/9, 4.21 FIP

The average of these nine seasons is a 6.88 K/9 and 3.84 FIP, and that sounds fair, at least to an extent. Guys like Wood, Rusch, early Cliff Lee, Wolf, and Lilly all seem to be decent comps for Erlin–flyballing lefthanders with solid command and at least one plus offspeed offering.

Wood doesn’t have as good of a curve as Erlin, but his changeup is better and he also chucks a solid cutter. However, he broke out late in the minors, unlike Erlin who has always been dominant. Rusch never quite had Erlin’s velocity or command, though the offspeed stuff and mechanical profile is similar. Vazquez’s season is probably fresh on everybody’s mind; he famously was terrible early in the year, then picked up some velocity and completely shut opponents down in the second half, so he’s sort of a weird outlier.

Lee’s an interesting case–he had decent stuff for a lefthander coming up, but his 2008 breakout came when he a) picked up 2 mph and b) started pounding the zone even more than he already was. That’s the power of an unexpected velocity jump, and if a similar thing happened to click for Erlin, then he could really take off. El Duque doesn’t really make much sense as a comparable on a mechanical/stuff level, though the statistical similarities are interesting. Wolf isn’t known for being this precise (3.23 BB/9 career), his curve is notably slower than Erlin’s, and he also has a slider, but many think Erlin will end up similarly. And hey, 24 career WAR is nothing to sneeze at.

I mentioned Arroyo above, and as you can see, he rebounded the next season in terms of strikeout rate–this was the year he moved to the Reds. Like Hernandez, he’s not the same sort of pitcher Erlin is, but the numbers do seem to end up in a similar place. Lilly is a guy I compare a lot of good-not-great lefties too, and I’m honestly surprised only one of his seasons fits the criteria. The main reason for this is that he’s actually been under 88 mph with his fastball every year since 2008, and his walk rates were elevated before 2007, so he only had one year in the “happy medium.” Like Wolf, he’s amassed a couple dozen WAR despite never being considered an ace. Finally, Schilling’s last season is on here. Schilling is a different animal than Erlin, with his main offspeed pitch being a splitter rather than the curve and change, and the “old pitcher skills” comment with Pedro also applies here.


I think we can all agree it’s a bit much to project Erlin to post Jered Weaver-esque numbers, and it’s probably underselling him to think he’s going to get Jon Garland-esque strikeout rates or post numbers as disastrous as Eric Milton’s in Cincinnati. While the pitchers in the “middle ground” don’t match up perfectly with Erlin either, they probably provide some reasonable context for his potential strikeout ability. As I mentioned, the mean strikeout rate of that group was 6.88 K/9, which is a far cry from the 9.7 Erlin has in his minor league career, but is nonetheless a respectable amount. There’s a chance he could surprise us and translate better than expected, like his San Diego teammate Cory Luebke, and there’s also a chance he could really struggle to miss bats in the big leagues for some reason, but that’s a fair place to start.

So, let’s calculate his FIP then. 6.88 K/9, so let’s say 688 K in 900 IP, and…wait.

How few walks is the guy going to allow? I started off by saying it’s a reasonably safe bet that it’ll be under 2.5, but by how much? Is he going to walk down near a batter per nine innings, like Fister, or is he going to be pushed up into the 2-2.5 realm?

This is an important question, because the pitchers in the sample average 2.20 BB/9. So while the seasons were all under 2.5, most weren’t under it by much. Only Martinez, Schilling, and Greinke were under 2.00, and the next lowest after that is Weaver’s 2.14 and 2.17. Everyone in the middle group save for Schilling was over 2.2. If Erlin will be under 2.2 while having the 6.88 K/9, he’ll likely beat the middle group’s mean 3.84 FIP.

And then, of course, there’s the matter of home runs–how many would he allow? Assuming a neutral park (not Petco, obviously) and average-ish luck (let’s say 8.8% HR/FB–average is around 9.5% and flyball pitchers tend to be slightly better at preventing homers), it would probably be around 1.05 HR/9 if he has a groundball rate around 35% and a strikeout rate around 7 K/9.

So, going back to our FIP formula, which of course is FIP = ((13HR+3BB-2K)/IP) + 3.13, we can plug in 105 homers and 688 strikeouts in 900 innings for Erlin, and add in different walk values.

1 BB/9 = 3.45 FIP
1.5 BB/9 = 3.62 FIP
2.0 BB/9 =  3.78 FIP
2.5 BB/9 = 3.95 FIP

My gut instinct is that since Erlin’s walked fewer batters in the minors than most of the group, he’ll also walk fewer in the majors, and I’d guess he’d be in the 1.8-2.0 range once he settles in. That would put him in line for a 3.7ish FIP if the strikeout rate and homer rates meet their projections. Petco could suppress the flyballs to the extent that he’ll be more in the 3.5 range there. That would make Erlin a rock-solid #3 starter–a lefthanded Shaun Marcum, if you will. After all, a 3.7 FIP would have ranked 53rd out of the 137 starting pitchers that threw 100+ innings in 2011, so we’re talking right around 60th out of the 150 starters in the league at any given time–a poor #2 or excellent #3.

I think that’s entirely within his reach, and we should leave open the possibility that like Luebke, Fister, Brandon Beachy, and others, he translates even better than that–after all, Ted Lilly’s maintained excellent strikeout rates with even less velocity and very similar offspeed stuff. Erlin’s flyball tendencies and average velocity will prevent him from being an ace, but there’s a strong likelihood he could be a mid-rotation starter on a first-division team, and he could even attain #2 status if he adapts well to the majors.

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