DAVID Cone is now a fifth starter and judged by that standard he was fine last night in his Yankee Stadium return. Today the Yankees need Mike Mussina to begin being who Cone was.

With Tuesday night’s rainout being rescheduled for June 4, Mussina is slated to face not only the Red Sox three straight times. But Pedro Martinez. The two have never faced each other. So this is Mussina’s pinstriped baptism. His chance to show he can have the steely spine that defined Cone in most of his Yankee days. His chance to show the Yankee decision was wise to spend on him last offseason and let Manny Ramirez go to the Red Sox.

Mussina has been OK so far. OK does not beat Pedro Martinez. It takes good stuff, both on the ball and inside. Martinez lost just six times last season. Andy Pettitte was the only pitcher to beat him twice. Pettitte is a Yankee, with a DNA full of victories. Now we really begin learning if Mussina is made of the same good stuff.

Though last night was supposed to be about Cone, Pettitte pitched better and the Yankees trounced Boston 7-3. The Yanks can assume first place today if Mussina can outdo Martinez.

Cone had entered to a standing ovation, which drowned out a few nudniks who booed. When this Yankee championship run is dissected, Cone will be one of the base pieces that propped it all up with his pitching, charisma and smarts. For that alone, he should have heard nothing but grateful cheers regardless of uniform.

Cone had made a pre-game determination not to acknowledge the crowd, to focus only on pitching. His fastball was alive early, topping out at a more-than-acceptable 91 mph. He also used a two-seamer that bent away from lefties and his slider hissed. Was he his old self? No. That guy is never coming back, lost in the brutality of thousands of pitches and a couple of surgeries.

But if you could ignore the name and history, and just think of Cone as a No. 5 starter – which is what he is now – his stuff was good enough. Yankee hitters were impressed and so was Cone, who in a post-game press conference said, “As far as movement and velocity this was the best I’ve been in a couple of years.” Before the session began, a Red Sox official removed a Yankee banner hung behind Cone; another part of the divorce.

His regrets were few, mostly centering on a 2-2 fastball he left up in the third and Bernie Williams turned into a two-run homer. He finished a nine-pitch fourth inning by schooling Alfonso Soriano with this four-pitch, all-strike sequence: curve, slider, fastball, split.

Cone wanted to be more economical and walked none to his five strikeouts. He permitted three runs in five innings, his fastball losing life late. He went to a three-ball count on just the final of his 23 batters after doing it nine times to 16 Twins in his first start of 2001 last week. He threw 85 pitches and the question now is whether he is building toward something – is there more stamina to be gained in that well-traveled arm and body? Even Cone conceded a smidgen of doubt.

The Red Sox are in a pennant race, one-half game up on the Yanks, and would love to have Cone’s savvy. But each pitch, inning, game is a minefield now. At 38, Cone is beyond borrowed time. He is in sudden death, desperately trying to preserve the baseball life he so adores. With Cone it is all what his body will allow because his heart is beyond reproach. Pettitte, a decade younger, lives in the same realm.

We still have to learn about Mussina, who at 32 decided to take the training wheels off his career and come to the big city. More than ever the Yankees are about their rotation. They have uncertainty in the bullpen, though they have so far refused Montreal’s request for lefties Randy Keisler and Alex Graman for Ugueth Urbina. Their offense has everyone edgy. The hardly seen George Steinbrenner was around, making life miserable behind the scenes. Paul O’Neill was furious before the game at what he thinks is too much attention being paid to his shortcomings when the problems are wide-ranging.

Ramirez is leading the AL in slugging and on-base percentages, reaffirming he is the sport’s best hitter. Mussina is 4-4 with a 3.75 ERA, a mixed bag so far. He is scheduled to face the best his next three outings, Martinez. Moments like this defined Cone as a Yankee forever.

Time for Mussina to begin showing us the same.

‘L’ OF A RETURN

How David Cone fared in his five innings of work last night at Yankee Stadium:

1ST INNING

Chuck Knoblauch struck out swinging.

Derek Jeter doubled to right.

Paul O’Neill struck out looking.

Bernie Williams hit by pitch.

Tino Martinez grounded out to catcher.

0 Runs, 1 Hit, 0 Errors

2ND INNING

David Justice grounded out to short.

Jorge Posada hit by pitch.

Scott Brosius struck out swinging.

Alfonso Soriano flied out to center.

0 Runs, 0 Hits, 0 Errors

3RD INNING

Knoblauch flied out to right.

Jeter singled to left center.

O’Neill flied out to center.

Williams homered to right, Jeter scored.

Martinez singled to center.

Justice struck out looking.

2 Runs, 3 Hits, 0 Errors

4TH INNING

Posada grounded out to second.

Brosius fouled out to catcher.

Soriano struck out swinging.

0 Runs, 0 Hits, 0 Errors

5TH INNING

Knoblauch flied out to center.

Jeter singled to center.

O’Neill singled to shallow left center, Jeter to third.

Williams grounded into fielder’s choice to second, Jeter scored, O’Neill out at second.

Williams stole second.

T Martinez flied out to left center.

1 Run, 2 Hits, 0 Errors