Scott Baker has played his entire major league career up until this point with the Twins. In seven seasons with the Twins, he has started 159 games and has posted a .570 winning percentage and a 4.15 ERA. Baker spent 2012 recovering from Tommy John surgery, but prior to that, there were a number of encouraging signs regarding his on-field performance. His strikeout rates were trending up, and his walk rates hovered around two walks per nine innings.
Below are Baker's strikeout rates over the course of his major league career.
As you can see, his strikeout rates have been trending up ever since he started pitching for the Twins. Research has shown that moving from the American League to the National League adds approximately .6 K/9 to a pitcher's record. If Baker pitches like he did in 2011, his K/9 rate would be in the 8.2 -- 8.7 range. For comparison's sake, Matt Garza posted an 8.95 K/9 in 2010, so Baker would be striking out hitters at almost the same rate as the 2010 version of Garza.
Below are Baker's swinging-strike rates. As we can see, Baker has consistently induced swinging-strikes at a rate higher than average (8.5%).
When it comes to strikeouts and walks, Baker is what you want in a pitcher. His ability to induce swinging-strikes and strikeouts, and limit walks makes him a valuable part of any starting rotation.
However, if that's where the discussion ended, Baker would have received more than a one-year deal. While teams were likely a little concerned with how Baker would return from Tommy John surgery, the success rate of this procedure is now near 95 percent. The biggest issue with Baker is his proclivity to give up the long ball. During his career, he has given up 1.16 home runs per nine innings, and has posted a 9.3% HR/FB rate which is about average (9.5%). The concern though is that he is going from what is known as a pitcher-friendly park to a hitter-friendly park. While that was definitely the case in 2010, the two fields' home run factors were much closer in 2011. Below are Wrigley Field and Target Field's park factors in the two seasons Baker pitched there: 2010 and 2011.
Below are a couple of hit charts that take the balls hit against Baker in Target Field and overlay them onto Wrigley Field.
In 2010 and 2011, there were a total of about five balls that would have gone for home runs at Wrigley that weren't home runs at Target Field. Baker will likely give up a couple more home runs at Wrigley than he did at Target, but it shouldn't be many more. The winds and temperatures of April and May should help Baker keep the ball in the yard, while June, July, and August will be a little less kind. The likely net result: it won't be as bad as these hit charts would suggest.
Something that should help Baker is his sinker. According to PITCHf/x, Baker used his sinker 57.5 percent of the time, and his slider 27.6 percent. Both of this pitches are known to induce ground balls at a high rate. However, the strange thing is that his ground ball rate is still at a middling 35 percent, well below the league-average of 44 percent. While I'm not sure what the reason for this is, it could be a result of his ineffective slider. His PITCHf/x pitch value per 100 pitches is at -1.13, which means that he gives up more runs on his slider than the average pitcher does. Chris Bosio's job should be to see what he can do to improve Baker's slider.
Baker's season will largely depend on his ability to keep the ball out of the bleachers. We know that he can strike out hitters at a healthy rate and limit walks. Whether or not he can keep the ball in the yard is something that will determine his future as a Cub as well as his value at the trade deadline.