This is how Fielding Bible rated the defense, compared to average fielders:

In 2009:
1B: Youkilis: +10 runs above average
2B: Pedroia: +12 runs above average
SS: Green, Lugo, Gonzalez: -22 runs
3B: Lowell, Youkilis combined: -17 runs below average
RF: Drew: +4 runs above average
CF: Ellsbury, -9 runs below average
LF: Bay, -1 run below average

The infield defense last year as a whole was rated 17 runs below average, thanks to the horrible defense at SS and 3B. The outfield as a whole was 6 runs below average, mostly because Ellsbury had a bad year in CF, playing too deep in my opinion, with a poor arm for CF.

Overall, the team was 23 runs below a team of league average defenders.

For this year, Scutaro was a +12 SS last year, Beltre was a +22 3B. Cameron was a +3 CF. In 2008, Ellsbury was rated as a +5 LF. If everyone repeats their numbers this year, the Sox defense would be:

1B: Youkilis: +10 runs over average
2B: Pedroia: +12 runs over average
SS: Scuataro, +12 runs
3B: Beltre: +22 runs
RF: Drew: +4 runs
CF: Cameron, +3 runs
LF: Ellsbury, +5 runs

Which comes to 68 runs better than average as a group. Or 91 runs better than last year’s group. Last year, the Sox allowed 736 runs.

IF the defense really is 91 runs better than last year, even if the pitching was exactly the same overall, they’d allow 645 runs. The runs allowed per game would drop from 4.54 to 3.98, which would probably be the best in the game.

Of course there are a lot of ifs here, and some people will reject the defensive numbers for whatever reason. But I think it’s very reasonable to expect the Red Sox to give up significantly fewer runs than last year. And Beltre’s a big part of that.

Now the offense is a whole different matter. And just adding Scutaro while moving Youkilis to third and keeping Kotchman at first would’ve upgraded the infield defense from horrible to good without adding Beltre.

The idea is that Beltre instead upgrades it from horrible to one of the best in the game. Should be interesting to see if that happens.

The guy does have great range, good hands, and an amazing arm, check out his highlights: