Tampa Bay Rays righty James Shields is seemingly turning in a mediocre performance in 2010. The 28-year-old owns a 6-7 record and has a middling 4.55 ERA, a combination that has led 11 percent on Yahoo fantasy players to pull the plug on the changeup artist. Is Shields struggling? Not really. But how bullish you are on his numbers improving depends upon your ERA estimator of choice.
In 99 innings pitched, Tampa’s 16th round pick in the 2000 draft has 8.36 K/9, 2 BB/9 and a 42.3% ground ball rate. That K rate is well above his career average of 7.29 K/9, while he’s basically matching his career totals in terms of walks and worm burners (1.94 BB/9 and 43.5 GB%, respectively).
Not much has changed in terms of his pitch selection or plate discipline stats. Shields is still leaping ahead in the count, getting first pitch strikes 61% of the time (60.4% career average, 58% MLB average). His contact rates aren’t drastically different, though he’s actually getting slightly fewer whiffs than normal — his swinging strike rate is 9.1% (10% career average, 8-8.5% MLB average) and his contact rate is 81% (78.8% career average, 81% MLB average). The cause of Shields’ increased K rate isn’t whiffs, but called strikes — his called strike percentage is 17.8% this season, compared to 16.7-17% over the past few years (17% MLB average). Called Strike% has a lower correlation with K rate than swinging strike rate, so it seems likely that Shields punch out rate comes back toward his career average (7.29 per nine). Zips projects 7.23 K/9 for the rest of 2010.
No huge, negative changes to this point. So, why the run-of-the-mill ERA for Shields? For one, he’s got a .339 BABIP this season, compared to a .310 career average. Opponents have hit a good deal of line drives against Shields this season — 21.5% (the MLB average is 18.9%, according to StatCorner). Two interpretations of that number come to mind.
On one hand, line drives falls for hits on balls in play more than 73 percent of the time, so that certainly contributes to the higher-than-usual BABIP. On the other hand, line drive rate is a rather volatile stat, and Shields’ career 19 LD% is right around the big league average. That suggests batters don’t typically scorch the ball against him. If his line drive rate comes back toward that career rate, his BABIP should fall. Shields has also allowed home runs on fly balls hit 14.4% time, well above his career 11.5% figure and the 11% MLB average.
Shields’ line drive and homer rate help explain the dichotomy between his tERA and xFIP. His tERA (tRA put on the same scale as ERA), is 4.43. tERA assigns an average run value to batted ball outcomes like line drives, ground balls, outfield fly balls and infield fly balls, as well as run values for K’s, walks, HBP’s and home runs. Liners and home runs obviously have a high run value, so a pitcher giving up lots of them like Shields is going to get dinged. Meanwhile, his xFIP, based on strikeouts, walks and a normalized HR/FB rate, is actually a career-best 3.50. xFIP sees strong peripherals and poor luck on fly balls, and expects considerable improvement.
Personally, I’d take the middle ground between those two figures. It’s unlikely that Shields allows so many liners or homers per fly ball hit against him moving forward. But it’s also unlikely that he continues to punch out so many batters. ZiPS thinks he’ll split the middle, too, with a rest-of-season FIP of 3.91. Shields is well worth owning in all formats — if he’s on the wire, snag him and expect a high-three’s ERA for the rest of 2010.
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