The most misleading pitching statistic is a pitcher's record.  Often times, pitchers will be saddled for losses when they pitched well enough to deserve a win.  The opposite is also true, where a pitcher can give up 5 runs in 5 innings and still get a win. 

A good example for this season is Johan Santana.  If you looked solely at his record, which is 7-7, you would say that he's had a down year.  And by the standards he's held up to, especially in NY, that is true.  But dig deeper into his numbers. 

His ERA is 2.96, which puts him 5th in the NL, and his 121.2 innings pitched puts him 3rd in the NL.  In reviewing his seven losses, the following has occurred:

Three of his losses have come when he's allowed one earned run (Atlanta, San Diego and Seattle), although he did give up a granny to a pitcher in the Seattle loss, but all those runs were unearned.   His last 3 no decisions, he has pitched 21 innings and gave up a combined 3 runs.  Not 3 runs per start, 3 runs total.  No doubt in each of those 3 starts, he deserved a W, and it's not his fault that the offensive offense put together by the "genius" Omar Minaya hasn't done squat for him.  In five of his past six starts, the Mets have scored two runs or less.  It's nearly impossible for a pitcher to pick up wins when your offense belongs in the minors.

Now, to take the opposite, let's look at Steve Trachsel from 2006.  His record in 2006 was 15-8.  Just looking at that record alone, it's a solid year.  We Mets fans who followed the run to the NLCS in 2006 know better.  His ERA that year...4.97.  Yes, an ERA of nearly 5 runs.  Now, is that a good year, or a byproduct of getting a lot of love from the first eight hitters of the lineup everytime he took to the hill?   His strikeout to walk ratio was nearly 1 to 1 (79 K's with 78 BBs) and 185 hits over 164.2 innings.  Digging deeper into Trachsel's numbers shows you that the record hardly shows what type of year he had.  And the Mets properly awarded him with nothing once the 2006 season concluded. 

The point is that records cannot be the sole gauge of how a pitcher is performing in a season, and the wins and losses are typically the first thing that is mentioned by broadcasters or the anchors on Baseball Tonight or whatever baseball show you may be watching.