No.
I mean, it depends on what you mean by "have to." Last Friday was a pretty typical day for Red Sox fans. The day was spent getting ready for the Pats game, dropping a few "r"s, and thinking that if the Red Sox hadn't done anything in the offseason, at least the Yankees hadn't done anything either.
Then the Yankees spun straw into gold. They turned A.J. Burnett into a 22-year-old with one of the best fastballs in the game. They turned Freddy Garcia into one of the most underrated starting pitchers in baseball. Where once the Yankees and Red Sox seemed to be heading for some mutually assured frustration with their top-heavy rotations, the Yankees done went and got better. Pretty rude. They probably broke a gentleman's agreement and everything.
Now the Red Sox are left with a rotation that features not one but two converted relievers. The third starter is a 27-year-old who has cracked the 100-inning barrier just once in four seasons. The Red Sox missed the playoffs last season because of an unfathomable starting-pitching collapse, and all they've done since then is lose two of those September starters -- one to Tommy John surgery, and one in a trade for a middle reliever. It might be addition by subtraction to lose John Lackey and Kyle Weiland, but it's all the Sox have done to help the rotation.
Well, it's not all they've done.
Red Sox officially announce Aaron Cook, Justin Germano signings.
So there's that.
The question posed in the headline isn't fair. Do the Red Sox have to get another starter? Not really. If they go into the season as is, they're still a supremely talented team. A flawed team, but still a team that can make a run at 900 runs scored with a couple of known quantities at the top of the rotation, and some impressive arms in the backend of the rotation. They improved the bullpen with a pair of trades, and their lineup is mostly intact. It's still a good team.
So by the standards of the rest of the world -- the standards of about 28 other teams or so -- the Red Sox are doing fine. They'll compete for a playoff spot. They should feel good about the talent on the roster. If they were just about any other team, they could be excused if they decided to walk away from the offseason, feeling mostly comfortable about their roster. So, no, the Red Sox don't need to answer the Yankees.
But the Red Sox need to answer the Yankees. It's more of a manufactured, invented need. On paper, the Yankees' rotation is stronger, and the lineup remains just as strong as last year, but the Red Sox have a strong team, and with the vagaries of baseball and the uncertainty of it all, they could contend for the division if a few things break right.
The problem with that is that "if a few things break right" isn't an acceptable clause in this particular arms race. These are the Red Sox. They're supposed to be better than "if a few things break right." It's going to be hard for them to keep pace with the team that finished seven games ahead of them last season, but it's pretty clear that they'll have to pretend they can. There's a waiting period for handguns, but not so much for hot-headed free agent contracts or trades.
The Red Sox will ignore that Roy Oswalt's back is held together with masking tape and watch springs. They'll make a huge push to sign him.
And if they can't sign him, they'll absorb Wandy Rodriguez's contract. And maybe they'll offer three or four prospects to see if the Astros will throw in Bud Norris too.
And if that doesn't happen, they'll give Scott Boras and Edwin Jackson that contract that the peanut gallery thought was impossible.
And if they don't do that, they'll dig through the old computer in Theo's old office and see if there's anything in the browser history that's blackmail-worthy. Enough for a Matt Garza, at least.
Remember that wacky idea that the Yankees were going to do something with their rotation? The same holds true, doubly so, for the Boston Red Sox. The odds of the Red Sox heading into 2012 with Alfredo Aceves and Daniel Bard in the rotation is comparable with the odds of Adrian Gonzalez shifting to right field so the Red Sox can sign Prince Fielder. There will be an upgrade. Whether or not whatever move they make is a particularly good idea is beside the point.