With Bobby Abreu’s contract option picked up, the Yankees have reduced the number of question marks in the 2008 lineup by one. There are still four mystery guests whose identity needs to be resolved, however.

C: Unknown (Jorge Posada, free agent.)
1B: Unknown (Surely not Jason Giambi.)
2B: Robinson Cano
3B: Unknown (Everyone but Red Rolfe has been rumored.)
SS: Derek Jeter
LF: Hideki Matsui or Johnny Damon
CF: Melky Cabrera
RF: Bobby Abreu
DH: Unknown (Matsui, Damon, Giambi, Shelley Duncan — or Ron Blomberg.)

One of the themes that has dominated the discussion of the Yankees’ options for 2008 during the brief off-season goes something like this: The Yankees had weak pitching last year, so they needed to score 968 runs to make the playoffs. Without Alex Rodriguez, they aren’t going to score nearly that many. But if they have better pitching, they won’t need to.

This is true, but we can’t know that the team will actually perform according to plans. One of the vexing things about projecting pitching is that it’s much harder than projecting offense. Hitters tend to have careers that are more linear than pitchers’. They reach a plateau of production and then turn in seasons that are a little better or a little worse. Occasionally, a hitter will have a fluke offyear, or have a Brady Anderson-style explosion. But on the whole, they will be within a safe range predicted by previous performances.

Most pitchers aren’t like that. Roger Clemens was a special pitcher not only because he was great, but because he was consistently great. More often, a team has to take its chances on someone such as Shawn Chacon. They might get the good Chacon, as the Yankees did in 2005 and the Pirates did this year; or they could get the evil Chacon, who seems to surface in years ending in an even number. Sometimes, a team can get neither good nor evil nor anything at all because the pitcher gets hurt. In 2006, Chris Carpenter made it through the season in working order and the Cardinals won the World Series. In 2007, Carpenter had to be sent back to the toy factory after just one appearance (maybe he had too much lead), crippling the Cards from the outset of the season. In short: The pitching gods are capricious.

That’s why it’s foolish to say that the Yankees can afford to go with a glove-only player at third base. One can assume that Phil Hughes, Joba Chamberlain, and Ian Kennedy will come through in 60% of their starts — but as good as that trio looks, it’s almost a sure thing that they won’t. Even if they do beat the odds, there are other reasons to be skeptical. Chien-Ming Wang seems likely to have another solid year, but Andy Pettitte just declined a $16 million option offer. Because Mike Mussina is under contract, the Yankees are almost obligated to give him another shot, but he’s already on his third strike: He’s been mediocre in three of the last four years. 2007 was worse than mediocre, and he turns 39 next month.

Meanwhile, Rodriguez was personally responsible for close to 16% of the Yankees’ total offensive production, and he saved a few more runs on defense. Losing him is like pulling Joe DiMaggio out of the 1941 Yankees. You can’t just blithely say, “Tra la, we’ll sign anyone and the pitching will take care of the rest.” Say the Yankees trade for White Sox third baseman Joe Crede. As Crede is coming off of back surgery, it’s unlikely that he’ll give the Yankees much more than his typical production — outside of 2006, that hasn’t been much, due to terminally low on-base percentages. Though he’s been a good defensive third baseman, he’s had the back surgery and he’s turning 30, so we can’t know for sure how much of his range remains intact. Let’s give him the benefit of the doubt, though, and say that his total production, offensive and defensive, will come to something like 70 runs. If all other elements are equal — that is, the rest of the offense does not improve or decline — then that would be akin to asking the pitching staff to improve from allowing 4.8 runs per game to 4.4, to improve from eighth in the league to fourth. It doesn’t sound like much. But given the uncertainties of a young rotation and an empty bullpen, it’s asking quite a lot.

It’s also asking Posada to come back and not fall off too far from his career-best season at 35, and asking that the four 33-year-olds in this year’s lineup — Matsui, Damon, Jeter, and Abreu — don’t get any older. At least one of them likely will. This is not the off-season for the Yankees to think they have such a surplus of offense that they can throw some away at any position. The only way to combat the unknowns of age and pitching is for them to add offense wherever they can. Both first base and third base are open. Having more than just a pretty glove at each would help the Yankees absorb the loss of Scott Boras’s most infamous client without having to pray for a pitching miracle.

Mr. Goldman writes the Pinstriped Bible for yesnetwork.com and is the author of “Forging Genius,” a biography of Casey Stengel.