After our introduction yesterday we can start with one of the positions that should contain one of the largest upgrades for the Red Sox. Adding Victor Martinez does not necessarily add much behind the plate, but it adds considerable value offensively. For now we will mainly use Martinez and Mike Napoli as they are the expected starters and either team's backup would be a downgrade.
Since there isn't really a good measure of catching defense I will pass on using that in this evaluation. This attempt by Beyond the Boxscore rates Jason Varitek and Mike Napoli as greater than 10 runs below average. In the comments they also rate Martinez as 10+ runs below average. There is no score for Jeff Mathis, but we will assume on this calculation they are all about a win below average and not give either team an advantage defensively.
AVG OBP SLG wOBA wRAA WARVictor Martinez
Victor Martinez .300 .379 .474 .372 23.5 4.5
Jason Varitek .209 .313 .390 .306 -8.0 1.2
Mike Napoli .270 .348 .485 .357 10.0 3.0
Jeff Mathis .213 .292 .313 .273 -12.3 0.3
Victor has caught with greater regularly since joining the Red Sox, in comparison to the rate in which the Indians were using him behind the plate. While he isn't a very good defensive catcher, Varitek is at best equal in defensive value, and ancedotal evidence suggests he's actually worse.
Even if Varitek was a competent, league-average catcher, the offensive difference between the two is astounding. The Red Sox upgraded went from a catcher with a .306 wOBA to one with a .372.
This season Varitek has been -8 runs above average for the Red Sox. In just the short 2 months since the trade Martinez has already accumulated 11.9 runs above average. Over a full season, Martinez is a 5 WAR* player while Varitek has deteriorated to a meek 1.2 WAR. A 4 WAR difference is a substantial upgrade for the Red Sox.
*Martinez lost value from positional adjustment by spending so much time at first base and DH. As a full time catcher his skills are worth 5 WAR.
Mike Napoli
Napoli was a bit of a thorn in the side of the Red Sox. His power is undeniable, but his on base skills are nowhere near that of Martinez. His wOBA currently stands at .357, which is above average, but still shy of Martinez in 2009.
He supplies about 3 WAR in a full season, which would be an advantage over the Red Sox if not for the deadline deal to drive Varitek to the bench. The acquisition basically flipped a 2 WAR advantage for the Angels into a 2 WAR advantage for the Red Sox.
Backups
Neither team wants to have to use their backups this series. Both are well below average offensively and quite possibly approaching replacement level. A start by either player severely hampers their team, regardless of any intangibles that could be rationalized, unless they can conclude that their defense is worth more than 2 WAR in a full season.
The Red Sox win this position easily. Napoli may hit a few homers in this matchup, but his lack of on base skills help give the advantage to the Red Sox 5-3.
Infield Matchup
Outfield and DH Matchup
Starting Pitching Matchup
Bullpen Matchup