No clubhouse is complete without a cancer, and Friday, on the occasion of their first game at Troubled Assets Relief Program Field (The TARP, for short), the Mets put the finishing touch on their brand-new clubhouse.

They added Gary Sheffield to the mix.

Don't get me wrong, I love Sheff. He will add some spice to a clubhouse that has an overwhelming smell of vanilla. For my purposes, and those of my colleagues, the coming of Sheffield to Flushing is the best news of the season so far. He could be our very own A-Rod.

But is the coming of Sheff truly the best thing for the Mets? I mean, for the amount of trouble he brings, they could have had Manny Ramirez. But not, of course, for the same money.

In true Mets fashion, they passed on Manny but jumped for mini-Manny. Now, here's what they get in return:

In his 21 major-league seasons, Sheffield, 40, has called seven clubhouses his home, and not one did he leave on friendly terms. At every stop, he has clashed with managers, general managers and owners. He has insulted teammates, reneged on contracts and, by his own admission, deliberately made errors to force his first team, the Milwaukee Brewers, to trade him.

He has ripped Latin players and players who didn't conform to his image of racial purity, such as Derek Jeter. He couldn't get along with Joe Torre, a man who could find common ground with Mahmoud Ahmadinejad. And just about every place Sheff has landed, he has found occasion to level a charge of racism at somebody, usually because their plans for Gary Sheffield differed from Gary Sheffield's plans for himself.

But all that can be forgiven for a player who has 499 home runs and 1,633 RBI in his career.

Here is Sheffield's unforgivable sin: He has not played the outfield regularly since May 29, 2006.

You read that right.

Now the Mets are bringing him in to do just that.

Either someone neglected to tell Omar Minaya that his team plays in the National League, which has yet to adopt the designated hitter, or the Mets believe that Sheffield somehow will be able to accomplish something I will go out on a limb and guess that no player in the history of major-league baseball has been able to do.

Namely, return to a full-time outfield position, after two years as a DH, at the age of 40.

This says a lot more about the Mets' confidence in Ryan Church than it does about Sheffield.

Admittedly, at a fire sale price tag of $400,000 — $1,000 less than they are paying Daniel Murphy — Sheffield looks like too good a bargain and too safe a gamble to pass up.

But wasn't one of the reasons the Mets passed on Manny their fear that his, um, quirky personality would disrupt their "clubhouse chemistry," which is none too stable to begin with?

The Mets apparently wanted no part of Manny the Malcontent, but what is Sheffield but a cut-rate malcontent, and probably washed up, to boot?

Surely the fact that the Tigers were willing to swallow hard on Sheffield's $14-million contract for 2009 should have been a clue to the Mets that Sheff does not have all that much left.

And if that wasn't enough, certainly Jerry Manuel's conversation with Tigers manager Jim Leyland — who, according to Manuel, said he needed a player with "more versatility" than Sheffield to spell regular rightfielder Magglio Ordonez — should have warned the Mets off.

Translated, Leyland was telling Manuel that Sheffield can no longer play the outfield.

Yet Minaya, whose love affair with aging, overpaid has-beens remains unrequited, has hired him to do just that.

Knowing Sheffield's history, you can only imagine how happy he'll be riding the pine watching Church play rightfield and flail against lefthanded pitching.

Having seen Sheffield play the outfield at Yankee Stadium, with its relatively conventional contours, one can only imagine the comedy and tragedy to come with him roaming around in right at The TARP, where some genius architect trying to contrive some genuine ersatz "character" in his cookie-cutter ballpark decided it would be a good idea to cut a bay window into the rightfield fence and overhang the second deck above it into fair territory.

Suffice it to say, The TARP will never be known as The House That Sheff Built.

He will show up Saturday, say all the right things, embrace familiar faces and leave nary a notebook unfilled.

That will last about as long as it takes him to decide he should be playing more, or that the manager doesn't like him, or the owners are too cheap, or that the GM has disrespected him in some way known only to him.

My guess is that by the All-Star break, Sheffield will be on his way to team No. 9.