1) The health of David Ortiz and Mike Lowell
Who cares about the catcher situation? This is what matters. If David Ortiz and Mike Lowell are healthy, the Red Sox are a team that makes the playoffs. Ortiz is just a year removed from his best OPS+ season ever (171 in '07), so please don't say he's washed up. Lowell is also a year removed from a World Series MVP trophy. Both are aging, but if they're healthy the middle of the Red Sox order is going to be dynamite.
2) The "low-risk, high-reward" signings
We know John Smoltz won't be ready for awhile, but let's keep our eyes on guys like Brad Penny and Takashi Saito. Penny and Saito are both "feeling good" (the most overused term in the history of Spring Training, by the way) but the results on the mound are what matters. If Penny and Saito can't get out Northeastern Huskies batters, then we know we've got a potential problem. But if these guys are lights out in both spring training and the regular season, how can anyone doubt Theo Epstein's strategy? There could be a day in baseball when you're more valuable after a bad season than a great season...
3) The shortstop battle
Jed Lowrie or Julio Lugo? We'll find out soon enough. Lugo, the overpaid veteran, has apparently been working hard this offseason trying to earn his job back. Meanwhile, Lowrie is recovering from a wrist injury that bothered him for a chunk of the '08 season. This is, essentially, a win-win situation for the Red Sox. If they both do well, perhaps the Sox could trade Lugo and install Lowrie as the fulltime shortstop. If one or the other struggles, we have a solid backup. The only way it looks really bad is if they both have horrible Spring Trainings ... but that couldn't happen, right? Right?