New York ? On the surface, all is well with the Yankees. Roger Clemens, Juan Rivera and Nick Johnson stood out in Wednesday’s 8-7 victory over the Kansas City Royals, which stretched New York’s winning streak to seven.

But just below, there are worries.

Mariano Rivera had another shaky outing, allowing four straight hits in a four-run ninth before striking out Desi Relaford to end the game with runners at the corners.

And with Jose Contreras rejoining the rotation this weekend, will Jeff Weaver be content with a bullpen role — or perhaps even a short stint in the minors?

“We’re trying to find out which way we are best,” Yankees manager Joe Torre said.

In the meantime, the Yankees are rolling. And the Royals are reeling.

Clemens earned his 305th win to tie Eddie Plank for 18th place on the career list, Juan Rivera hit his first Yankee Stadium home run and threw out a runner to help stop Kansas City’s rally in the ninth, and Johnson hit a two-run homer and scored three runs.

New York completed a three-game sweep and improved to 10-0 at home against the AL Central this season.

But the ninth inning left an uneasy feeling.

After Angel Berroa’s one-out RBI single off Sterling Hitchcock made it 8-4, Mariano Rivera relieved. Mike Sweeney drove in a run with a dribbler to third that went for a single, Carlos Beltran grounded a run-scoring single up the middle and Raul Ibanez singled sharply to right.

Sweeney held up at third, but Beltran took a wide turn at second and was thrown out by Juan Rivera, brought back from the minors after Tuesday night’s game.

“When I saw him hit the ball, I took off,” Beltran said. “I was going full speed when I saw Sweeney (hold up). It was three or four steps past second base. It was tough for me to react and get back. It’s not something to be sorry about. That’s the way we play the game.”

Royals manager Tony Pena said Beltran shouldn’t be criticized for running aggressively.

“It was a little mistake we made. It’s no big deal,” Pena said. “He thought Sweeney was going to score, and he wanted to go to third with the tying run. It’s not something I’m going to crucify him for.”

Joe Randa singled to center for Kansas City’s seventh straight hit, pulling the Royals within a run. Rivera then struck out Relaford on three pitches for his 27th save in 33 chances.

Mariano Rivera said it seemed the ball had “eyes today.” Catcher John Flaherty thought the closer might have missed a few spots.

“It’s not like they’re hitting the ball to the gaps or on the fence or over the fence,” Rivera said. “They put the ball in play and it went through the holes. … Most of the time, I’m going to come out on top.”

Last weekend at Baltimore, Rivera allowed homers in consecutive appearances for the first time in his career, including a game-tying drive to Luis Matos. Rivera has blown four of 11 save chances in the first 20 days of August, numbers he’s not accustomed to.

“He is the elite,” Torre said. “Whatever year it is, ’98, ’99, 2000, I’m no different in my feeling and confidence in him.”

Kansas City, which outhit New York 17-13, has lost six of eight.

Clemens (12-7) allowed three runs and eight hits in 6 1/3 innings. The 41-year-old right-hander, 8-2 in night games but just 4-5 in the afternoon, left with two on in the seventh and was replaced by 46-year-old left-hander Jesse Orosco, who struck out Brent Mayne. Orosco walked Aaron Guiel, then Antonio Osuna came in and struck out Berroa.

It was the first start for Clemens since he talked about the possibility of pitching for the United States in next year’s Olympics. He intends to retire after the season and said he wouldn’t pitch in the major leagues next year just to stay in shape.

“It’s not something I’m thinking about at this point,” he said of a possible Olympic bid.

Clemens fell behind 2-0 in the second inning, but New York quickly overcame that against Jimmy Gobble (2-2), making his fourth major league start. Derek Jeter had a go-ahead, two-run single during a nine-pitch at-bat in the four-run second after falling behind 0-2 in the count.

Gobble started his big league career with two wins over Tampa Bay but has since lost to Minnesota and New York. He gave up eight runs and 11 hits in 4 1/3 innings, his ERA rising from 3.52 to 6.41.

After Randa’s sacrifice fly and Ken Harvey’s RBI single put the Royals ahead in the second, the Yankees quickly ate up Gobble.

“I thought I made some pretty good pitches that they hit hard,” he said. “And the pitches I missed, they hit harder.”

Notes: During the game, New York announced Contreras will return from the disabled list and start Sunday against Baltimore. Weaver will either go to the bullpen or be optioned to Triple-A Columbus until Sept. 1. … Clemens struck out five and took over the AL lead with 164.