I was asked a question in the comments, and thought the answer was worthwhile to post.
Can you get me this piece of information, I don’t know how to find it? How many groundballs to the right side of the infield has Wieters hit this year? It seems like he rolls over an inordinate amount of balls which tells me he is trying to pull outside pitches too often among other issues."
Checking things out:
Wieters has hit the ball on the ground more than the average batter this year; his groundball rate is about 47% and the league average is around 44%. It's been a bit higher batting right-handed than left-handed (which seems to be the side the question is directed at), but it's pretty close to 47% for both.
FanGraphs splits their data up into left-center-right instead of pull or opposite field, so I made a quick adjustment there, splitting center into left and right by the proportion of left to right already shown*.
* So if it's 10 ball hit to left, 12 to center, and 20 to right, I moved 8 of the center ones to right (12 * 20/(20+10)) and the remaining 4 to left. It's not exact, but it's not terrible (I hope).
Of the 132 groundballs Wieters has hit this year, about 88% have been to the pull side; 86% left-handed and 95% right-handed. According to this
piece, major league batters pull grounders about 72% of the time. The highest figures they had for lefties (from 2006) was from 83-88%, and for righties it was 87-93%. Obviously the sample sizes for Wieters aren't huge - using his career numbers the rates drop to 84% left-handed, 80% right-handed, and 83% overall - but it's still more than most hitters. The Tampa Bay Rays sometimes employed the infield shift against Wieters, and you can see why.
Combining the 44% groundball rate, the 72% groundball pull rate, and an average overall pull rate of about 61%, we get* that major league batters hit about 52% of the balls they pull on the ground, and only 28% of the balls they push on the ground. For Wieters in 2010, about 64% of the balls he's pulling have been on the ground (65% lefty, 61% righty).
* Algebra! Seriously though, these are all very rough approximations.
Wieters has been a bit of pull hitter overall this year (~64%, compared to last year, when he went to the opposite field about as often as he pulled the ball), and when he pulls the ball it's going on the ground quite a bit. When he's gone the other way though, he's been a flyball hitter (just an 18% groundball rate).
This is part of the reason his home run numbers are so low - you get more power pulling the ball, but when he does that it hasn't gone in the air often enough. In fact, of his 19 career home runs, more than half have been hit to the opposite field. That speaks to Wieters power potential, and now the key is to make the necessary adjustments at the plate that can get him some more loft to his pull side.
So it seems like Bret may be right. Instead of going with those outside pitches as he did last year, Wieters might be rolling over and pulling them on the ground. It looks like pitchers are taking advantage by attacking him down and away more. Presumably this is what a hitting coach is for, right?