NEW YORK (AP) - Mike Mussina kept turning around to see poorly hit balls find holes in the Yankees' defense, his body language conveying just a touch of exasperation. By the time he walked off the mound after the first inning, Kansas City had a three-run lead.

''His luck wasn't real good in the first,'' manager Joe Girardi said, ''but it changed after that.''

Helps when your offense wipes out the deficit - and then some - in a hurry.

Jason Giambi hit a grand slam, Alex Rodriguez sent a three-run homer bouncing into Monument Park and New York broke loose against Brian Bannister and the Royals in a 15-6 rout Sunday that salvaged a split of the season series.

Cody Ransom added a two-run homer and Xavier Nady also went deep for the Yankees, who totaled six runs in the previous two games but got that many in the first inning alone. Rodriguez finished 3-for-3 with five RBIs, and Derek Jeter went 4-for-4 and scored three times.

''They got out to a three-run lead and we had a real good first inning,'' Rodriguez said. ''That's really the key to our offense.''

Mussina (16-7) settled down after the shaky start, retiring his last 14 batters and improving to 6-0 against teams from the AL Central. It was win No. 266 for the right-hander, tying him with Bob Feller and Eppa Rixey for 34th on the career list.

Despite winning at least 15 games 11 times, Mussina has never been a 20-game winner - something he could certainly accomplish if the Yankees get on a roll.

''That's probably the fourth time I've given up a couple in the first inning and we came back,'' he said, praising the offense rather than himself. ''I don't want to try that too much.''

Ross Gload hit a two-run homer and Billy Butler had a two-run double for the Royals, who wasted two chances over the weekend to win their first season series against New York since 1999. Instead, they've lost nine of 11 after a modest three-game winning streak.

The Yankees (66-58) closed within five games of Boston for the AL wild-card spot. They open a six-game trip Tuesday at Toronto, and will play 22 of their final 38 on the road - all but 10 of those games against teams with winning records.

''We have our backs up against the wall and every game is very important,'' Rodriguez said. ''You've got to take it like it's the last week of September.''

A-Rod struck the first big blow, a drive to left that bounded off the concrete beyond the wall and rattled around like a pinball among the stone monuments. His 28th home run tied the game at 3, but a miserable afternoon was only beginning for Bannister.

The right-hander served up a 1-1 pitch to Nady moments later that he drove off the foul pole in right. After a visit to the mound by pitching coach Bob McClure , Robinson Cano singled, Jose Molina hit a run-scoring double and speedy youngster Brett Gardner - who had the winning hit in the 13th inning Saturday - tripled for a 6-3 lead.

''I knew right away it was going to be tough,'' said Bannister, who didn't manage another out after retiring Johnny Damon to end the first inning. ''Missed over the plate and every time it hurt me.''

Jeter singled and Bobby Abreu and A-Rod each walked to load the bases in the second for Giambi, who hit his second grand slam of the season into the appreciative Bleacher Creatures in right.

Nady followed with an infield hit and Cano a double down the line, finally chasing Bannister (7-12) after one of the worst starts of his career.

''Just a lack of command and control,'' Royals manager Trey Hillman said, ''and probably at this point confidence.''

Rodriguez added a run-scoring single in the third, and Abreu and A-Rod each drove in runs in the seventh before Ransom's fourth career homer into the left-field seats.

Bannister wound up allowing 13 of the 16 batters he faced to reach safely, on 10 hits and three walks, and the 10 runs he yielded were a career high. His ERA in four starts against New York ballooned to 15.07, and he's allowed 30 hits and six homers in just 14 1-3 innings.

''Since I was a little kid, I wanted to pitch in this ballpark, and it hasn't been that nice to me in return,'' he said. ''It kind of leaves a bitter taste in your mouth.''

Notes: Jeter was hit by a pitch just below the left elbow in the seventh inning but remained in the game. ... Giambi's 14th slam tied him with Gil Hodges , Mark McGwire and Mike Piazza for 14th on the career list. A-Rod is tied for eighth with 16. ... Yankees DH Hideki Matsui (left knee) took 15 at-bats in a simulated game and could be activated from the disabled list Tuesday. ... Royals OF Jose Guillen , a huge football fan, tried to win over some New York fans when he sported a Brett Favre jersey.