I'll try and run these every so often throughout the baseball season when I've got a spare minute or two.

Over Performer:

Fred Lewis

First, let me say that Fred is not a bad player by any means. In fact, he's a very serviceable outfielder; he's just not the .324/.405/.529 (AVG/OBP/SLG) player that he's masquerading as now. Let's break it down a bit shall we?

Fred has an otherworldly and likely unsustainable Batting Average on Balls In Play (BABIP )* of .405 . His line drive percentage (LD%) is 16.9, which gives him an expected BABIP (xBABIP)** of .289. Clearly Lewis is running into his fair share of good luck. That being said, he does have speed and will likely continue to outperform his xBABIP a bit with an above average amount of ground ball, infield hits. Still, there is no reason to think that he'll be able to maintain a .405 BABIP too much longer.

Using his xBABIP and 75.5 Contact Percentage (CT%)**, his component batting average is .235, which gives him a component line of .235/.328/.402. [Note: you can find a cool Component Batting Average calculator here .]

Does this mean I think he's a .230 hitter? No. And as I said up top, I don't think he's a bad player at all; he's got decent plate discipline and has shown throughout his Minor League career that he can maintain a good BABIP. He'll provide you with a decent number of runs and steals atop the Giants order, but he certainly isn't a .320/.900 OPS guy. If you've got him on your team, now might be a good time to seek out a less savvy owner that likes the look of his current lofty numbers and deal him for someone of greater value.

Under Performer:

Nick Swisher

Swisher is batting .208/.357/.317 on the year. His his Home Run/Fly Ball (HR/FB%) is down (9.7% compared to a career 14.%), which might explain part of the low AVG, but It's certainly doen't deserve all of the blame. His LD% is a healhty 22.4%, which would lead one to believe that more than any thing else, his low AVG is a result of some bad luck. Sure, Swisher has never carried a high batting average, but a 22.4 LD% puts his xBABIP is .344, far better than his current .244 BABIP. A quick look at his .277/.413/.396 component line should tell you that he's not one to be given up on; and with him installed at the top of the White Sox' order, he'll be great source of Runs for the rest of the year.

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*Generally speaking, any batter dramatically over/under his career BABIP will regress to his mean. The average BABIP is usually around .300 at the major league level. An unusually high or low BABIP is usually an indicator of good or bad luck.

** Contact Percentage = (AB+SF+SH-K)/(AB+SF+SH)

***xBABIP can be quickly calculated by adding .120 to a players LD%