New York ? After another shaky start, Mike Mussina became unhittable in a hurry.

Mussina settled down and lasted seven innings, Hideki Matsui hit a go-ahead single in the seventh, and the New York Yankees won their sixth straight Sunday with a 4-2 victory over the Kansas City Royals.

Opponents were hitting a hefty .344 against Mussina coming in. And midway through the fourth, he had given up eight hits and two runs.

Then he retired 11 batters in a row.

“I was frustrated,” Mussina said. “I thought I was pitching better than two base-runners an inning. You have to realize every inning is a new inning, and every hitter is a new hitter.”

The Yankees completed a three-game sweep of the Royals, who have dropped four in a row and 14 of 17. They fell to 1-10 on the road this season.

“With a pitcher like Mussina, if you’ve got him set up for the knockout punch, you’d better deliver it,” said Mike Sweeney, who drove in both runs for the Royals.

Trailing 2-0 with runners at the corners in the third, Mussina (2-4) got Ken Harvey to ground into an inning-ending double play on a nice stop by second baseman Miguel Cairo.

Matsui doubled and scored on Cairo’s sacrifice fly in the bottom half, and Jason Giambi tied it an inning later with a homer into the upper deck against Jeremy Affeldt (0-3).

“No question, any time you face a good pitcher, you’ve got to get to him early,” Royals manager Tony Pena said.

Kansas City threatened again in the fourth on one-out hits by Benito Santiago and Desi Relaford. The runners advanced on an infield out, but Mussina retired Angel Berroa to end the inning.

The right-hander did not give up a hit after that.

“It looked like once he got a little tired, he pitched better,” said Joe Torre, who earned his 800th win as Yankees manager. “He gets in a rhythm. He hung in there and got better.”

Mussina took the 2-all tie into the seventh, then the Yankees took the lead.

Jorge Posada opened with a double and scored on a single by Matsui, who went to second on the throw to the plate. Matsui advanced on a wild pitch and scored on Ruben Sierra’s sacrifice fly.

“They just broke through on me in the seventh,” Affeldt said. “Posada … I don’t think he could have hit it in a better place, and Matsui put it right in the hole. It’s not like he hit it hard.”

Hard enough.

The two-run cushion was plenty for the Yankees’ bullpen. Tom Gordon worked a scoreless eighth, and Mariano Rivera got three outs for his ninth save in nine chances. He retired three straight batters with two on to end it.

Carlos Beltran tripled into the right-field corner with one out in the first and scored on a grounder by Sweeney. In the third, Beltran doubled and came home on Sweeney’s single to left.

Affeldt allowed four runs and eight hits in 6 1/3 innings.

Notes: Torre is the fifth Yankees manager to reach 800 victories, following Joe McCarthy (1,460), Casey Stengel (1,149), Miller Huggins (1,067), and Ralph Houk (944). … The Yankees received their 2003 AL championship rings in a pregame ceremony. … Royals LF David DeJesus took extra-base hits away from Sierra in the third inning and Bernie Williams in the fourth, running down drives in front of the 399-foot sign in left-center field. … Williams returned the favor, making a sliding catch in center on a drive by DeJesus in the seventh.