Six weeks after disappearing from the Yankees’ lineup with a bum left foot, aging slugger Jason Giambi is out of his walking boot and shaking off the cobwebs in Tampa. There is no guarantee that he can play again anytime soon — after tearing your plantar fascia, your foot is mostly held together by wishful thinking — but what is certain is that a year and a half remains before the Yankees can buy out the one-dimensional slugger’s contract. If Giambi is certified to play, the Yankees have to take him back, no matter how much dislocation that causes.

Giambi’s defensive game had long ago deteriorated to deplorable levels, making him often resemble nothing so much as an actor in a rubber Godzilla costume while tending first base. At 36, he wasn’t going to get better. Having been hobbled, it’s likely that he will now be significantly worse. The Yankees had limited him to the designated hitter position by choice prior to the injury. That restriction will now be mandatory.

That is not to say that having Giambi back is automatically a bad thing. With the exception of his injury and illness-riddled 2004, Giambi has always hit for the Yankees. Thanks to his home run power and great patience at the plate, he’s been a terrifically productive player even after permanently shucking the .300-hitting aspect of his repertoire after the 2002 season. Coming into this season, his career rates as a Yankee were .266 AVG/.415 OBA/.535 SLG. It doesn’t matter that what the Yankees intended to get was the Giambi who hit a cumulative .308/.412/.545 for the Oakland A’s. Where it counts, Giambi has been all hitter.

The return of Giambi, whenever it happens, would seem to be all positive. It’s not, but only because the Yankees will almost certainly lack the intestinal fortitude to pull the plug on Johnny Damon when the sluggish slugger comes back. Damon, 33, is ostensibly a center fielder, but as a Yankee has displayed diminished range and an arm that is all too reminiscent of Bernie Williams. With Melky Cabrera showing great range and a rifle throwing arm in center — in 1,732 career games in the outfield, Damon has 66 assists; in 219 career games in the outfield, Cabrerahas21 — the Yankees have wisely decided that it is in their best interests to play their top defensive outfielder at the most demanding outfield position. This is notable — the Yankees pretended that Bernie Williams could play center for years after he no longer was an asset; that Damon is not entitled to the same deference from this veterans-can-do-no-wrong ballclub is an unexpected miracle of clarity.

The team has disposed of Damon by taking his season-long slump and installing it at designated hitter, a position at which Damon has hit an anemic .237/.338/.325 (collectively, designated hitters are batting .262/.351/.437 this year). It’s hard to fault the team’s reasoning — Damon has a track record of producing, they lack alternatives, and he’s signed through 2009. They can’t just put him in cold storage, so they might as well use him and hope he remembers how to hit.

The problem is that there is a strong likelihood that he might not. Putting aside Damon’s age and a career pattern of having on and off years, a lot of what made Damon useful immediately prior to coming to the Yankees was his ability to profit from hitting in Fenway Park. In four years with the Sox, Damon was a .310 hitter at home, but a .281 hitter on the road. It was likely that he would leave a good part of his offensive cachet in Beantown.

That was exactly what happened, though it took a September slump to make that prediction hold true. Damon batted 300/.371/.515 through last August before crashing to .200/.287/.300 in September. Along the way, Damon set a career high in home runs, which served to mitigate any concerns about his batting average. It now appears that the power surge was a fluke. It was the September fadeout that was the real harbinger for 2007.

What we don’t know is if the Yankees accept that conclusion. Even without the dubious incentive of Damon’s contract, many teams, if placed in a similar position, would give the veteran an entire season’s worth of rope, believing that 33 isn’t that old, and surely the .300 hitter of days past will emerge with time.

Giambi’s return will force the Yankees to reconsider that position. As the Yankees make their desperate run at the wild card or a 1978-style upset of the AL East division-leading Red Sox, a power spike can only help — as a team the Yankees are no better than the middle of the pack when it comes to home run potential, and even then, much of that potential resides in the person of Alex Rodriguez. If Giambi has anything left he will surely out-hit Damon, especially in the home run department.

That should spell the end, at least temporarily, of Damon as a starter. Surely the Yankees wouldn’t bench the improving bat (. 302/. 363/.4 41 since May, through Monday) and defensive wizardry of Melky Cabrera so Damon can play center, thereby damaging their present and their future. Sure they would, which is why Giambi’s return is a threat in so many ways — a threat to the pennant race opposition, to Damon , and to the Yankee s themselves.

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