I love coming up with bold predictions. Not those off the wall ones that have like a 1% chance of happening, but those that have been built upon a shred of reality and have a reasonable chance (say 20%) of coming true. It is especially fun when everyone is either optimistic or pessimistic about a player and you’re prediction argues the opposite of the crowd. I am guessing that this particular prediction doesn’t quite sit at that level though, but I would say it is still pretty bold nonetheless. As a result of being traded to the Rangers, Ryan Dempster will be worthless in standard 12-team mixed leagues the rest of the season.
Let’s start out by talking about what he has done for the Cubs so far this year. First off, his K% is down this year and at its lowest rate since 2007, his last year as a reliever. Although his SwStk% has improved from last season’s career low mark, it still sits well below what he had posted in previous seasons. So basically, it validates the drop in strikeout rate. Also likely hampering his ability to punch batters out is a loss of fastball velocity. He is averaging below 90.0 miles per hour for the first time in his career and it represents a nearly 1.0 mile per hour drop from last year, which itself was down from 2010. This all makes it unlikely that Dempster was going to see any kind of rebound in strikeout rate over the rest of the season.
Next, his ground ball rate sits at an all-time low, as he has essentially swapped them for line drives. Obviously, that is not a good trade-off. His LD% sits at a career high 24.4%, so it would seem like hitters are teeing off on him. Yet amazingly, his BABIP is actually lower than his line drive rate, something you rarely see! If he’s not inducing pop-ups or an extreme number of fly balls, how exactly has he managed to maintain a .242 BABIP? Beats me! So that magic act he is pulling with his BABIP is going to end and bring down his career best LOB% along with it.
When you put his entire skill set together, you’re left with a 3.84 SIERA, nearly identical to what he’s done every year since he’s returned to the rotation. His luck has bounced all over the place though as his ERA has ranged from this season’s current 2.25 mark all the way up to last year’s 4.80. While we can say last year was probably just some terrible fortune, this year seems to be the exact opposite. So, even if he were to stay in Chicago, the final two months may have been very unkind to Dempster.
Now he moves to the American League, and as we know, that will reduce a pitcher’s strikeout rate and increase his ERA on average. If that’s not scary enough, he’s now calling the AL’s best hitter’s park home. Over the last three years, Rangers Ballpark has inflated run scoring by 19%, right-handed home runs by 23% and left-handed home runs by 31%. Wrigley Field of course is a hitter’s park as well, but not to the same degree as the bandbox in Texas. Wrigley has increased run scoring by a more modest 8%, been neutral for right-handed homers and boosted lefty home runs by 11%.
According to UZR/150, the Rangers defense is rated just ahead of the Cubs, but Dempster is going to see a BABIP regression regardless. So the bottom line is that even if he had stayed a Cub, the warning signs abounded. Now when you combine the regression he should have already been expected to experience in ERA with the unfavorable changes in league and home ball park, you have the potential for a massive rest of season disappointment. Unless he gets fantastic run support (which admittedly may very well happen) leading to a bunch of lucky wins, he may be very close to being worthless in mixed leagues.