Fantasy Baseball: 5 Pitchers Who Must Build Off a Strong Second Half

Blake Treinen, RP, Oakland Athletics

We've been comparing first-half and second-half splits here, but for Oakland Athletics reliever Blake Treinen, it's worth looking at his 2017 season before getting traded and after getting traded.

Treinen had proven to be a dependable reliever for the Washington Nationals in recent years, but like most of their bullpen in the first half, he was horrible. His 5.73 ERA was unsightly, but it looked like he wasn't enjoying a whole bunch of luck, either -- the right-hander produced a 3.78 SIERA with a 27.3% hard-hit rate and 60.5% ground-ball rate allowed with the Nats. And while his 18.9% strikeout rate was a little low, his 7.7% walk rate was much improved from the prior two years (11.4% in 2015 and 11.8% in 2016).

Once he got sent west in July, the results started coming. His SIERA improved significantly to 3.04, but not as much as his ERA, which settled in at 2.13. His walk rate stayed the same while his strikeout rate jumped up to 26.9% and he experienced the regression he was hoping for in the BABIP department, watching that mark go from .381 with the Nats to .299 with the A's.

He saw a huge difference in his slider while relying on his fastball less -- after throwing his breaking ball 19.8% of the time in Washington, that number jumped to 31.2% in Oakland. The value of this offering, per Pitchf/x, went from -1.4 to 7.6.

It was also helpful to put himself in a position to succeed more often, as his first-pitch strike rate jumped from 53.3% before the trade to 66.0% after. This is all notable because he could be a sneaky source of saves next season with Oakland after nailing down a save in 13 of his 16 successful opportunities with the A's this past season.