Seattle Mariners: Yusei Kikuchi may be on the verge of a breakthrough

Yusei Kikuchi showed a number of improvements last season for the Seattle Mariners.

The Seattle Mariners will soon face one of the more unique contract situations in baseball right now with starting pitcher Yusei Kikuchi, their 29-year-old left-handed pitcher who has greatly underperformed expectations during his first two seasons in a Mariner uniform.

The conclusion of the 2021 season ends the three-year/$43 million portion of Kikuchi’s contract, in which the Seattle Mariners can then pick up a four-year/$66 million option. If Seattle declines, Kikuchi can exercise a one-year/$14.5 million player-option.

If both decline, Yusei Kikuchi becomes a free agent after the 2021 season.

Most Seattle Mariners fans would likely agree that Kikuchi hasn’t lived up to those kinds of contract numbers but his second season in the big leagues was much-improved compared to his rookie season and there are a handful of signs that may point to a potential breakthrough in 2021 for Yusei Kikuchi.

The Mariners are certainly hoping these small sample numbers are a sign of something bigger before having to make a tough decision immediately after the conclusion of next season.

Seattle Mariners saw an improved Yusei Kikuchi in 2020.

First, the overall numbers aren’t great. If you look at the back of Kikuchi’s baseball card, you see a career 8-15 record with two seasons of a 5.00+ ERA, and a career 1.47 WHIP with a .283 average against.

But let’s look a little deeper at some of Kikuchi’s 2020 numbers that point to the possibilities of an even more-improved 2021 campaign.

Kikuchi recorded a 5.17 ERA across his nine starts last season, but his 3.30 FIP was one of the biggest disparities among starting pitchers last season, meaning there had to have been a bit of bad luck thrown in there, more than what the average pitcher faces in a season.

If you take a look at Kikuchi’s Baseball Savant numbers, they are more impressive. He was able to avoid barrels, ranking in the 86th percentile in the majors and his expected weighted on base average was nearly 20 points lower than his actual wOBA, which ranks in the 71st percentile.

Combine that with his big spike in ground balls, up to 52% from 44% last season, and a significant drop in home runs allowed (2.00 HR/9 dropped to 0.57 HR/9) and you would think his baseline numbers would look different.

Opponents did hit Kikuchi hard, but they were hard groundballs with a high probability of being turned into outs, outs which didn’t happen with the defense behind him. While the Mariners infield defense was a middle-of-the-pack unit, Seattle’s outfield defense ranked 25th in terms of Outs Above Average (-7).

But to be fair, Kikuchi didn’t help himself much in certain areas. While his strikeout rate jumped from 16% to 24% and his swing and miss rate on strikes (12%) was a significant jump compared to his rookie season, Kikuchi struggled to throw strikes.

His walk rate was 10.3% and he failed miserably at throwing first-pitch strikes. His 50.5% first-pitch strike rate ranked 109th among 111 pitchers who threw at least 40 innings in 2020. Keeping the ball on the ground and producing swings and misses are keys to success, but when you let hitters get ahead more than half the time, the walks pile up and those unlucky bounces turn into disasters and crooked numbers on the scoreboard.

Overall, there were big improvements across the board for Yusei Kikuchi in 2020. Not many pitchers ended the season worth 1.1 Wins Above Replacement with an ERA over 5.00.

His fastball velocity is up nearly three mph to 95 mph now, he ditched the curveball for a cutter that produced a 25% whiff rate, a .230 xBA, and just one home run (most oft-used pitch at 40%), and three of his four offerings recorded a whiff rate north of 30%.

If Kikuchi can find the strikezone more in 2021 and continue the improvements he made last season, he may be on the verge of a breakthrough for the Seattle Mariners. Whether or not he’s worth $60+ million over the next four years is a different discussion, but he could end up becoming a reliable rotation piece for Seattle next season.