It's been said long and often that the two fatal flaws of John Jaso were that he's bad at catching and that he can't hit lefties. I can't definitely refute the defense one. I do think that Jaso is a sub-par defensive catcher. His numbers seem to convey that. However, the numbers that are available also convey that he's not a disaster back there, merely mediocre.
The hitting lefties thing though. That deserves a more thorough examination. Here are John Jaso's career platoons.
Yep, that looks pretty bad.
Except there's something very important here, sample size. Notice how few plate appearances Jaso has had against lefties? 151. That's roughly about one month's worth. In the first 149 plate appearances of the 2012 season, Albert Pujols posted a .510 OPS. You wouldn't conclude from that split that Albert Pujols couldn't hit anyone, would you? Stuff happens over samples that small. It's not gospel.
If that was all the info we had, the reasonable, informed opinion to take would be an agnostic one and state that while the evidence looks poor, we can't be confident how well or poor Jaso fares against left-handed pitchers.
That's not all the info we have. We also have his minor league splits.
Or in total.
Wow, look how irredeemably awful John Jaso is at hitting lefties. Or, wait... what? Over a larger sample size, there's actually not much of a difference at all. An 85-point difference in OPS is actually smaller than the MLB average in 2012 among lefty hitters, who saw a 100-point drop in OPS facing a southpaw.
Jaso's minor league numbers don't trump his major league ones. They add to the picture. And because they cover a much larger sample, they should be the first point of reference. And what it portrays is that Jaso is more likely to be a perfectly normal hitter when it comes to platoon splits.
If only someone would give him a chance.