His promotion to the major leagues may be just days away, and Saturday night Zack Wheeler gave the Mets no reason to believe he is going to need much more seasoning. Pitching for Triple-A Las Vegas in Fresno, Calif., the Mets’ next big thing went six innings and allowed three hits and one earned run while striking out six. Wheeler, who left the game for a pinch hitter with a 2-1 lead in the seventh, threw 95 pitches, 62 for strikes. The stud right-hander is expected to make his major league debut as soon as the Mets’ next homestand. He entered last night with a 3-1 record and a 4.13 ERA for the 51s.