Maybe it's not the pitching

Red Sox pitchers, entering play Wednesday, had accumulated an ERA of 4.68. Red Sox starting pitchers, entering play Wednesday, had accumulated an ERA of 5.59.

Starting pitching was supposed to be the strength of this Red Sox team. Now, all of a sudden, we're getting all excited because Josh Beckett and Justin Masterson are turning in back-to-back "hardly dominant" but effective starts. Beckett has an ERA of 5.85. Jon Lester has an ERA of 6.51. Brad Penny, going into his start Wednesday, had an ERA of 6.69.

There's only so much pitchers can do, though. If they strike a guy out, great -- and Red Sox pitchers have 285 strikeouts, second-best in the American League. If they walk a guy, that's not great -- and Red Sox pitchers have 149 walks, fourth-worst in the American League. (Their strikeout-to-walk ratio is 191, just slightly above the league average.)

But if the ball gets put in play, then what happens? Couldn't defense play as much of a role in this as pitching? The Rangers and Mariners have played their way into contention on the strength of great defense. The Red Sox, as it turns out, have shot themselves in the foot with lousy defense at key positions.

Here's one indication: The Red Sox pitching staff has an opponents' BAPIP (batting average on balls put in play) of .311, 11 points higher than the league average. Lester's opponents' BAPIP is .385; Beckett's is .352. Even Justin Masterson's is .350 -- and he's a sinkerball pitcher who should be seeing infielders feast on the ground balls he's inducing.

Here's another: Ultimate zone rating.

Like a few of the stats that are making their way into the public consciousness -- or, say, football's quarterback rating -- it's difficult to define Ultimate Zone Rating. The basic idea is to measure the number of outs a player records (and, thus, the number of runs a player prevents) in his particular area of the field.

Suffice to say, a fielder with an UZR of 4.0 has saved his team approximately four runs; a fielder with an UZR of -4.0 has cost his team approximately four runs.

Let's look at the UZR leaderboard so far this season:

First base
1. Chris Davis, Texas: 3.9
7. Kevin Youkilis: 1.4

Second base
t-1. Ian Kinsler, Texas: 5.4
t-1. Rickie Weeks, Milwaukee: 5.4
10. Dustin Pedroia: 1.4

Shortstop
1. Marco Scutaro, Toronto: 4.9
18. Nick Green: 1.2

Third base
1. Ryan Zimmerman, Washington: 6.7
18. Mike Lowell: -2.0

Right field
1. Jay Bruce, Cincinnati: 8.0
12. J.D. Drew: -0.3

Center field
1. Mike Cameron, Milwaukee: 7.8
9. Jacoby Ellsbury: 0.8

Left field
1. Nyjer Morgan: 8.3
16. Jason Bay: -9.0
(No big-league left fielder has a worse UZR rating than Bay.)

We could try another rating, too: The Fielding Bible's plus-minus rating. Plus-minus measures a player's ability to get outs against an average defensive player at his position. The higher the plus-minus number, the more outs the player has recorded. So far this season:

First base
t-1. Billy Butler, Kansas City: +5
t-1. Kevin Youkilis: +5

Second base
1. Ian Kinsler, Texas: +10
t-8. Dustin Pedroia: +3

Shortstop
1. Marco Scutaro, Toronto: +12
t-19. Nick Green: 0

Third base
1. Ryan Zimmerman, Washington: +13
33. Mike Lowell: -9

Right field
1. Ichiro Suzuki, Seattle: +6
t-3. J.D. Drew: +4

Center field
t-1. Matt Kemp, Los Angeles: +7
t-1. Chris Young, Arizona: +7
22. Jacoby Ellsbury: 0

Left field
t-1. Matt Holliday, Oakland: +7
t-1. Nyjer Morgan, Pittsburgh: +7
31. Jason Bay: -2

By both measures, the Red Sox have gotten average defense in center field (Ellsbury's first-inning catch on the warning track on Wednesday notwithstanding), below-average defense at shortstop, and absolutely miserable defense at third base and in left field.

The thing is, though, Bay and Ellsbury have exactly zero errors to their credit this season. According to the statistic that most influences a pitcher's ERA, Bay and Ellsbury are perfect fielders -- but according to In the outfield, if you don't get to a ball, you almost never get charged with an error -- but that means every ball Bay doesn't get to turns into a hit for which his pitcher is charged.

And remember the Saturday afternoon a week and a half ago when Lester induced what seemed like six straight slow ground balls only to see every single one of them roll into left field between Lowell and Julio Lugo? Lester was charged with six earned runs in that inning despite allowing only one hard-hit ball; no errors were charged to anyone. But if one or two of those ground balls had been fielded and Lester had escaped that inning unscathed, his ERA would be 5.36 right now as opposed to 6.51.

That's how much impact defense can have on a pitching staff.

And that might be why Boston pitchers are having so much trouble.