In the summer of 2010 Justin Morneau was on his way to another MVP season, posting 5 WAR by July. During a game against the Blue Jays that all changed, when he got kneed in the head by Toronto infielder John McDonald. He didn't play again that season, and hadn't been the same since. This year it looks as if that maybe has changed.
After missing the rest of the 2010 season, Twins fans didn't know what to expect heading into the 2011 season. Morneau never really got over the concussion like symptoms, and there wasn't a ton of optimism in Twins Territory. As it turns out Morneau wasn't healthy, and had a disappointing 2011 year. His offense was all but gone, his ISO was a career low .106 and his 69 wRC+ was a career low. There were some bright spots though. His walk rate was 3% than his career average, but his strikeout rate was right at his career average. His line drive percentage dropped four percentage points, going from 22% in 2010 to 18.5% in 2011, and he has had a slight increase in his groundball percentage.
While Morneau has only played in 12 games this season, he has had some nice improvements. His walk rate is right at his career average, but his strikeout rate is 10% higher. As the season goes on that should decrease. His power looks as if it could be back, his ISO is at .311 but that should decrease a good amount. He may never have his old power, but an ISO of .190 doesn't seem out of the question. His batted ball profile is a little skewed right now, his line drive percentage is only at 12% and his groundball percentage six percentage points above his career average. While everything has looked good so far, it's hard to say how he'll turn out in the end.
Every concussion is different, for example look at former Twin, Corey Koskie. Before he got his career ending concussion he was a 5 WAR player. Once he got that concussion he was out of baseball in a couple seasons. Hopefully for the sake of Twins fans Morneau stays healthy. So far he's been a big part of the Twins success on the offensive side, and in order for them to stay effective he will need to continue to stay healthy.