Number 1
2013: Orioles trade SP Jake Arrieta and RP Pedro Strop for SP Scott Feldman
Wow, cover your eyes, Orioles fans! While Jake Arrieta was an incredible pitcher for the Cubs and a big part of their World Series title in 2016, he was largely a disappointing and overhyped starting pitcher for Baltimore.
The Cubs capitalized on a career from Scott Feldman to acquire these eventual stars, who was similarly disappointing in Baltimore. In 15 starts with Baltimore, Feldman finished with a 4.27 ERA with 65 strikeouts, departing in free agency the following year to Houston. Arrieta went on to win the Cy Young during his 2015 season, transforming into the ace scouts long proclaimed him to be in Baltimore.
Including Strop in the deal was a bit head-straching, who was in the midst of a down year after many years of being a reliable bullpen arm with electric stuff. Strop was a key bullpen arm in the 2016 World Series run, and posted a sub-three ERA during six of his seven seasons with the Cubs.
Overall, this was an absolute fleece for Chicago that provided them key pieces for their 2016 World Series roster.