Snyder may not be available until the offseason. Either way, Snyder is a better option for the Red Sox than Martinez.
Martinez is the superior player.
He's hitting .287/.368/.467 with 14 home runs this season. He's behind only Joe Mauer and Brian McCann in catcher OPS.
His fatal flaw is his defense. He's played only 50 out of 95 games at catcher due to superior defense from Kelly Shoppach. Martinez has only thrown out 13 percent of runners this year and has only thrown out 24 percent in his career. He's allowed 39 stolen bases this year.
Snyder is the opposite.
When he received consistent playing time last year, he threw out 31 percent of base runners, a more significant difference than it looks like. It's only four percent less than Yadier Molina last year, who won the Gold Glove.
Although he struggles with the bat, hitting .224/.354/.381, the Red Sox need the defense. Jason Varitek has allowed 73 stolen bases in 73 games, and he's only thrown out 15 perecnt of runners.
That looks even worse when you see the high-velocity pitchers he's caught for such as Josh Beckett, Jon Lester, and Brad Penny, who has reached 96 MPH recently.
The need for offense comes from a seemingly underachieving and inconsistent lineup. Despite being currently seventh in runs in the majors, Jason Bay, JD Drew, David Ortiz and Dustin Pedroia aren't as good as they were last year.
However, the core of the lineup isn't as bad as it looks.
Bay has an OPS+ of 123. Drew is on pace for 100 walks, which could make him one of the league's better lead-off hitters. Ortiz is coming out of his slump. Pedroia, who improves as the year progresses, has an OPS of 1.034 in July.
Adding LaRoche improves the offense, but Snyder would improve the defense a lot more than Martinez.
The Rays and Phillies were the best defensive teams last year, which led them to the World Series. Superior defense and stolen bases put the Rays above the Red Sox in the ALCS last year. Defense is a need.
Snyder is a much lower risk and would also come cheaper than Martinez. An AL East team would rather send prospects to the NL West than the AL Central. Snyder also has lower trade value than Martinez.
I'm not against building an all-star team. But Snyder brings the defense that the Red Sox need, which Martinez doesn't have.
Stats provided by www.fangraphs.com.