New York ? Willie Randolph and Mel Stottlemyre enjoyed their day as co-managers of the New York Yankees.

After all, Ruben Sierra and Jon Lieber made it an easy afternoon.

Sierra homered twice and drove in seven runs, and Lieber looked great in his long-awaited Yankees debut, leading New York over Kansas City, 12-4, Saturday.

Hideki Matsui also connected and had three RBIs for the Yankees, who have won a season-high five straight following a four-game skid.

Their latest victory came without manager Joe Torre, who was attending his daughter’s Holy Communion ceremony. Randolph, the team’s bench coach, and Stottlemyre, the pitching coach, ran the team in Torre’s place.

“It was real strange because I’m used to sitting next to Joe,” Stottlemyre said. “Willie and I had a lot of fun today. We scored runs early, my pitcher was throwing strikes and our defense made some nice plays. It was a great deal of fun, but I missed Joe.”

Sierra hit a three-run shot off Eduardo Villacis in the third inning and a grand slam off Curtis Leskanic in the eighth, earning a standing ovation from the crowd of 54,103 and a curtain call.

Sierra’s seventh career slam landed in the upper deck in right field, giving him 16 multihomer games. And he was robbed of two more RBIs when center fielder Carlos Beltran made a diving catch in the sixth.

“I’ve been feeling good since last week. I’ve been hitting the ball hard,” Sierra said. “Right now it looks like everybody is coming around. It’s a good sign.”

The Royals got shortstop Angel Berroa and slugger Juan Gonzalez back, but lost for the 13th time in 16 games. They dropped to 1-9 on the road and 7-15 overall, last in the AL Central.

“This ballclub is much too good a ballclub to keep playing like this,” manager Tony Pena said. “We’re going to come back tomorrow and get started. Watch out! Watch out! Somebody’s going to pay.”

A 20-game winner with the Cubs in 2001, Lieber (1-0) made his first major league appearance since Aug. 1, 2002. He didn’t pitch last year after undergoing Tommy John surgery on his right elbow, and began this season on the DL with a strained right groin.

Working quickly and wearing Roger Clemens’ old No. 22, Lieber retired 15 of 16 batters during one stretch. Handed a 5-1 lead in the third inning, he got 13 groundball outs and pitched into the eighth.

“I feel like I got a second chance right now and I just want to make the most of it. It’s just been a long road. I just want to give back as much as I can,” Lieber said. “It’s an honor just to be a part of this team.”

It was a big boost for the surging Yankees, counting on Lieber to be a reliable fifth starter.

The right-hander allowed three runs and five hits in seven-plus innings. He struck out three, walked none and threw 69 of his 91 pitches for strikes.

Paul Quantrill gave up a two-run double to Mike Sweeney in the eighth.

Matsui also homered off Villacis (0-1), who made his big league debut after getting called up from Double-A Wichita. He lasted only 3 1-3 innings.

“He left a few balls up. He showed a good changeup and a good curveball at times, but he was inconsistent,” Pena said.

Lieber gave up a loud double to Beltran in the first inning and an RBI groundout by Gonzalez. But the Yankees went ahead on Gary Sheffield’s run-scoring infield single and Matsui’s RBI groundout.

Villacis walked two in the third, and Sierra lined an 0-1 pitch over the right-field fence for his first homer of the season, making it 5-1.

Matsui led off the fifth with his third of the year, and Enrique Wilson added a sacrifice fly.

Jason Giambi reached base in all five plate appearances and Derek Jeter added three hits for the Yankees (13-11), two games over .500 for the first time this season.

Matt Stairs homered off Lieber in the seventh.

Villacis gave up five runs, six hits and four walks. He started in place of Darrell May, who left last Saturday’s game against Minnesota with discomfort in his left groin.

Notes: Berroa, last season’s AL Rookie of the Year, came off the disabled list and went 1-for-4 with two strikeouts. He had been out with migraine headaches. … Gonzalez returned to the lineup after missing four games because of the flu. … Yankees OF Kenny Lofton, on the disabled list with a strained right quadriceps, is expected to rejoin the Yankees on Sunday. He went 1-for-3 Saturday in the second game of a minor league rehabilitation assignment with Double-A Trenton. … Alex Rodriguez extended his hitting streak to 12 games, longest by a Yankees player this season. … Randolph said Torre made out the lineup Friday night. … Sierra also had seven RBIs on Aug. 8, 1995, with the Yankees against Baltimore. His last grand slam came June 21, 2002, with Seattle at Houston.