Chien-Ming Wang got the news from pitching coach Ron Guidry that he will start the Yankees’ playoff opener, and the young pitcher responded in his typically low-key manner.

“Gator told him and he sort of shrugged his shoulders: Okay,” Joe Torre said. “I’m sure there will be some butterflies on Tuesday when they start introducing people, but this kid doesn’t let you know how he’s feeling.”

In announcing his rotation yesterday, Torre said Mike Mussina will follow in Game 2 and that Randy Johnson, bothered by a bad back, will pitch Game 3, most likely on the road at Minnesota or Detroit. Torre didn’t say whether Jaret Wright or Cory Lidle would start Game 4, if it’s needed.

Johnson was scratched from his final regular-season start to give his back a chance to rest. The 43-year-old left-hander has been bothered by his back throughout the season, and it’s gotten worse recently.

“With the back situation, I want one good game out of him,” Torre said.

Wang entered yesterday’s start against Baltimore with an 18–6 record and a 3.57 ERA, going 10–3 with a 2.88 ERA at Yankee Stadium. Given the Yankees’ high-priced, star-filled roster, it would have been a long shot in spring training to predict Wang would open the playoffs.

“Not when you have Randy and Moose here,” Torre said. “I don’t think he could ever dream of that.”

Mussina is 14–7 with a 3.57 ERA (8–2 with a 3.30 ERA at home) and Johnson is 17–11 with a 5.00 ERA (10–5 with a 5.01 ERA on the road).

Torre’s other big decisions will be whether to play Jason Giambi or Gary Sheffield at first base, and to choose between Hideki Matsui and Melky Cabrera in left field. The designated hitter is likely to come from among Giambi, Sheffield, and Matsui.

“I told the players last night, I said basically: ‘We have a lot of talented people here, and I don’t know what the lineup’s going to be. Just understand that,’ ” Torre said.

Giambi, bothered by a torn ligament in his left wrist, returned to the lineup as a designated hitter yesterday and homered for the first time since August 20. Sheffield, coming back from wrist surgery on June 13, made his major league debut at first base on Friday night.

“Both guys have good hands. Sheff looks like he may have a little more range,” Torre said. “That’s going to be probably the toughest decision to make when you’re writing the lineup down.”

Matsui broke his left wrist May 11, returned as a designated hitter Sept.12 and played his first game back in left field on Tuesday.

Torre is leaning toward emphasizing defense in left over hitting, which gives Cabrera an edge.

“Melky is better than Matsui, but Matsui certainly isn’t marginal. He knows how to play it, and he can go catch it and he gets great jumps on the ball,” Torre said. “Matty doesn’t scare me with any stretch of the imagination, but the other kid has a better arm and gets to more balls.”

With all his injured players back, Torre had a batting order yesterday that began with Johnny Damon, Derek Jeter, and Bobby Abreu, continued with Alex Rodriguez, Giambi and Sheffield, and finished with Matsui, Jorge Posada, and Robinson Cano — who began the night with a .343 average.

Bernie Williams was on the bench.

“In all honesty, I don’t know that there would be a better lineup than that in postseason play offensively. That doesn’t mean they can’t be beaten,” Orioles manager Sam Perlozzo said. “You pitch a little bit, you can beat anybody.”