New York ? Randy Johnson knows his mission: Win and nothing else.

The Yankees imported the Big Unit last winter to be their ace, snuff out opponents and get New York its first World Series title since 2000.

With the best-of-five AL playoff series against the Los Angeles Angels tied at one game apiece going into Game 3, the 42-year-old left-hander sounded determined as he prepared for his Yankees postseason debut.

“I understand that I am here to get this team over the top,” he said. “And with that, there’s no making mistakes. I made a few during the regular season, and unfortunately there’s no room to make a lot of mistakes during the postseason.”

It wasn’t clear whether the game would be played as scheduled tonight at Yankee Stadium or be pushed back by rain, which is forecast for three straight days.

Johnson has been the one constant in New York’s

conveyor-belt pitching rotation, and Alex Rodriguez has said repeatedly the 6-foot-10 lefty would be the difference in October.

After struggling with his mechanics for 41â2 months during his first season in the Bronx, Johnson found his form after discovering on video that he was rushing his delivery and dropping his arm.

He went 6-0 with a 1.92 ERA in his final eight starts, and from July 26 on held left-handed batters to an .074 average (4-for-54) with one extra-base hit, a double by Boston’s David Ortiz in New York’s AL East clincher last Saturday.