By R.J. Anderson //

When it comes to wins, James Shields has always had tough luck. Despite an ERA of 4.01 over his first 118 starts (his career total entering this season), Shields had only won 43 games, and had 36. Part of that was because of blown wins by his bullpen. Baseball-Reference keeps track of the times a pitcher leaves a game in line for the win only to see his bullpen blow it. That happened eight times to Shields entering 2010.

This off-season, the Rays upgraded the bullpen, spending $7 million on new closer Rafael Soriano (2.71 FIP) and finding a hidden gem in new set-up man Joaquin Benoit (2.00 FIP). Shields figured to benefit from those moves. Yet he’s actually in the midst of the worst season of his career if you go solely by ERA (4.90), and still struggling in the win-loss department (8-9). Still, here are the two reasons why you should go out and acquire Shields or at least refuse to sell low.

1) The ERA is skewed.

By nearly every other pitching metric Shields is actually having one of, if not the best season of his career. FIP, which simply weighs walks, strikeouts, and home runs allowed; xFIP – which adjusts for home run rates; and SIERA, which includes groundball rates, all suggest Shields is one of the league’s better pitchers this season. So why is his ERA so off? Well, in part, because of one really horrendous start. On June 11, Shields completed only 3.1 innings against the Florida Marlins, allowing 10 earned runs. Take that one start out of the equation and Shields’ ERA drops from 4.90 to 4.31. Which leads us to reason number two.

2) The home run rate isn’t sustainable.

There’s a point in a pitcher’s career when you can accept that maybe he does give up more home runs than the average starter. That point never occurs over the span of one season. Take the batted ball data from Shields’ pre-2010 career and compare it to this season. His home run per flyball rate is more than 3% higher. There is no reason to believe the same pitcher who has upped his strikeout rate is suddenly more hittable. Further, his home run per outfield flyball rate (as opposed to infield flies) is even higher.

When in doubt, go with the larger sample size. And in this case, that sample size suggests Shields is going to be a worthwhile pickup in the second half.