Alex Rodriguez can’t do it alone. For some, this will be a stunning statement, given that it implies he was doing “it” at all — it being the dirty business of winning ballgames. Now, Rodriguez hasn’t always deigned to immerse himself in that business, particularly last year, and even in the first few games of the 2007 season when he was stranding runners with his usual style. It was only on Saturday that the old MVP form reasserted itself, with two home runs, including a walk-off grand slam.

What’s less certain is how long the MVP form will stay, and even if it does, if the Yankees have given themselves the offensive and pitching depth to sustain a long run of winning. On paper, the Yankees are solid and should score liberally while maintaining decent if unspectacular pitching. Already, though, this whole equation has been thrown into question by injuries to Chien-Ming Wang, Hideki Matsui, and Johnny Damon, as well as poor performances by all of the starting pitchers in the first games of the season.

While it’s too early to be truly concerned with the Yankees’ 2–3 record, the sight of Miguel Cairo starting in left field should be of great concern. For all of Brian Cashman’s manifold strengths as general manager, when it comes to the major league bench he has always had a cavalier attitude bordering on neglect. The eternal monument to the Yankees’ disregard for the importance of depth is the 2001 World Series, a contest that history was begging New York to win for reasons beyond sport that don’t need to be detailed here. The Yankees went into that World Series with one arm tied behind their backs, shackled with reserve players like Clay Bellinger, Enrique Wilson, and an all-but-retired Luis Sojo.

This year’s Yankees have only Cairo in the Bellinger class of empty suit, but that’s only for lack of trying. Because of the enlarged pitching staff made necessary by carrying the uni-dimensional Mike Myers and the Cerberusstyle first base/designated hitter rotation, the Yankees have the most shorthanded, inflexible bench in the majors. This was obvious even before the season started, but it should have been painfully apparent as soon as Johnny Damon’s calf put him on the bench. The Yankees opened the season with only four outfielders, Melky Cabrera being the sole reserve. With Damon down but not disabled, they were down to three. When Hideki Matsui strained his hamstring they had two. Kevin Thompson, who took Matsui’s roster spot, brings them back to three, meaning the team is still in danger of being short an outfielder if Bobby Abreu takes another ball off of his knee or Cabrera runs into the wall.

The lack of depth neuters Joe Torre as an in-game manager — his strategic options for pinch-hitting, pinch-running, and defensive substitution are largely nonexistent or self-defeating. He can pinchrun for Jason Giambi, but only after Giambi is last at bat. Otherwise, he risks having a non-hitter like Cairo, or a singles hitter (at best) like Mientkiewicz up in the ninth inning.

More importantly, on select days it takes the team’s greatest asset, its offense, and cuts its potency nearly in half. Cabrera showed last season that at this stage in his career he can be an average player. He showed potential production. The actual good stuff only surfaced periodically, and even that disappeared altogether in September when he slumped badly. That he has continued that slump into the new season raises the possibility that the league has caught up with him. Cairo is a poor hitter for an infielder. In the outfield, he’s a bad joke; there are dozens of minor league outfielders, including Kevin Thompson, who can outproduce him. That’s not to say that Thompson can be much more than a once-a-week stopgap reserve.

Throw in the first base platoon — for which the best-case scenario is sub-par production — and, as happened yesterday (Jorge Posada’s scheduled day off), the team is left with a lineup that is no longer a threat to score a thousand runs. It’s not even imposing. Reserve catcher Wil Nieves will struggle to get his on-base percentage above .250.

Matsui’s injury put him on the disabled list, but it seems that his absence will be brief. Damon could be back as soon as today. Posada will be back from his sabbatical. Still, some things won’t change. The first base platoon is what it is. Posada will have more days off. There will almost certainly be more injuries at some point.

The Yankees survived their injuries last year in part because Philadelphia’s Pat Gillick was kind enough to hand them Bobby Abreu at a steep discount. There’s no guarantee that they will be the recipients of similar largesse this year. In the long run, this week’s struggles may prove to have been insignificant, but that outcome is far more likely if the team takes them as a hint to be better prepared when the next star has to hit the trainer’s table.

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