Over at SI.com, Cliff takes a look at more off-season signings and how they might play out:

Mike Cameron, CF, Red Sox

The 2009 Red Sox’s dirty little secret was that, save for the perpetually underrated J.D. Drew (10.5 runs above average in right field per UZR), their outfield defense was a disaster. That Jason Bay was 13 runs below average in left field may not have been a huge surprise, but Jacoby Ellsbury, having finally taken over center field full time with Coco Crisp in Kansas City, was even worse. Ultimate Zone Rating listed Ellsbury as 18.6 runs below average in center, a shockingly poor performance for a young player known for his speed. Together Bay and Ellsbury cost the Red Sox three wins in the field, which is one reason why Bay was allowed to sign elsewhere and Mike Cameron was brought in to play center and push Ellsbury to left.
Cameron’s center field defense has been worth almost exactly a win for the Brewers in each of the last two seasons, while Ellsbury played 346 1/3 innings (less than a quarter of the time he spent in center last year) in left field in 2008 and was nearly a win above average in that brief time. Don’t expect that sort of brilliance from Ellsbury this year, but even if he is merely worth one win over a typical 1,200 innings, the Red Sox could experience a whopping five-win upgrade on defense alone. Some of that will be given back in the downgrade from Bay’s bat, which was worth five wins in 2009 according to VORP, to Cameron’s, which is typically worth roughly half of that, but that massive upgrade on defense keeps the Sox’s new outfield arrangement well above replacement, and well above their 2009 performance.

Estimated upgrade: 2.5 wins