The appeal of Bard might be that he could hit v RHP well enough to give Flores a break a couple of times a week, at least, and keep Flores fresh, while he is 3 or 4 years younger than Valentin and is a regular catcher. Flores tailed severely 2d half of the year. First half he was acceptable offensively (.750 OPS IIRC).
The problem with Bard is that, while he played hurt most of the year, his numbers v RHP last year were awful. Compare vs. RHP the past 3 years:
2006 - .333 / .411 / .519 (BABIP .369 - some guys have all the luck)
2007 - .250 / .329 / .361 (BABIP .284 - welcome back to Earth)
2008 - .230 / .312 / .286 (BABIP .259 - what goes around, comes around)
Career is closer to 2007.
Flores v. RHP
2007 .220 / .276 / .297
2008 .238 / .285 / .368
Career .232 / .282 / .347
Valentin looks better than Bard as a switch hitter v. RHP but do people see him as the sole backup catcher anymore?
2006 .286 / .318 / .476
2007 .274 / .322 / .373
2008 .271 / .342 / .430
If Valentin made the roster, would he take Nieves place or be primarily 3d catcher and PH?
Oh, and as for the guy the Sox right now are keeping ahead of Bard - George Kottaras - a 25 year old lefty power hitting, decent OBP catcher with some experience catching a knuckler in AAA. Defensively questionable.