Assuming Christian Yelich returns from his knee contusion fairly shortly, here is an interesting question posed by Marlin Maniac manager Ehsan Kassim:
More valuable by the end of the season, Christian Yelich or Dee Gordon?
Both players are certainly trending in opposite directions for the Miami Marlins. On one side, Yelich has been fantastic since June, having hit .305/.372/.422 (.352 wOBA) through the last two and a half months. That line is a little better than the one he put for most of last year; he has hit 24 percent better than the league average over this time period.
What has keyed this resurgence? With all things Yelich, it comes back down to plate discipline. Yelich established himself as something of a savant at taking pitches and working counts. However, this year Yelich has seen fewer pitches than he did in 2014, when he ran up 4.26 pitches per plate appearance. He is down to 4.07 pitches per plate appearance this year, which is far below both last year and his overall career numbers.
However, if you recall, the early-season back injury certainly appeared to affect Yelich. Does anything change when you break Yelich's game down by month?
Yes, things do change, but not in the way that you expect. Yelich has trended towards swinging more as the season progresses, meaning that he has decided that swinging more often has been the key to improving his numbers. His overall contact rate has improved, as it was up to 83 percent in the month of July. However, are the extra swings the cause of this? When you look at the trends of the contact rates, the extra swings do no superficially appear to be the cause; the added contact appears to strictly be on out-of-zone pitches rather than in-zone pitches. Yelich's in-zone contact rates have stayed between 76 and 87 percent this year with no trends.
Where are those swings occurring? Pitchers are throwing more often out of the strike zone on the outer lower corner of the plate, and Yelich has been offering more at that pitch than he did last season. The following is a chart comparing where Yelich is swinging more or less often this year than he was last season.
You can see that the trouble is all in that lower outside corner for Yelich, as he is taking a lot more swings at those pitches. The zone has not seemingly changed with the adjustments from June and July either.
Could the decrease in the number of pitches per plate appearance be associated with the change in zone rate? Pitchers appear to be throwing fewer pitches in the zone against Yelich. It would make sense for him to adjust to swing at fewer pitches, but that does not appear to be occurring. From April to July, Yelich has not really adjusted the amount of total swings, though the location of swings in and out of the strike zone have vacillated. If anything, you would think that Yelich would try to see more pitches once pitchers threw fewer shots in the zone at him. If anything, it is going in the opposite direction.
Ultimately, this drop in pitches per plate appearance is most likely associated with Yelich's hitting success. He is getting more contact and more swings for hits, so that is ending plate appearances earlier than expected. That means that this trend does not really help us describe Yelich's success. What it does mean is that, knowing Yelich's ability to adjust, he will have to make further changes to his fluid plate discipline game in order to maintain his balance. As of right now, Yelich's strikeout and walk rates have improved since the early part of the season and have returned to his 2014 levels in June and July, likely in part due to his adjustments and work at the plate.
Those adjustments, when combined with Yelich's good defensive value, can still form an excellent package for the rest of the season. Both Baseball Prospectus and FanGraphs' many projections systems are expecting Yelich to put up about one win for the rest of the season, leaving him at somewhere between 2.5 to three wins worth on the year. In order for that total to beat Gordon, the latter would have to continue playing at replacement level, but he has done that essentially for the past two months. The overall odds for that are pretty low, but it is tremendous progress for Yelich to have even recovered to this extent given his sub-replacement play for the first two months of the season. His adjustments are still ongoing, but he is making a slow climb back up to respectability and above-average play.