NEW YORK (AP) _ Anthony Rizzo remains out of the Chicago Cubs' lineup against the New York Mets because of tightness in his back.

Ian Happ is set to start in Rizzo's place at first base again Tuesday night in the opener of a pivotal three-game series. Chicago entered with a one-game lead over Philadelphia for the second NL wild card, while the Mets were two back.

Cubs manager Joe Maddon and president of baseball operations Theo Epstein acknowledge Rizzo could miss the entire series. If he is able to return against the Mets, it would most likely be in the series finale Thursday, according to Epstein.

Rizzo left Saturday's game against Washington in the fifth inning and sat out Sunday. Chicago had a day off Monday.

Rizzo is batting .290 with 25 homers, 82 RBIs and a .928 OPS.