When Jayson Nix saw Derek Jeter go down and not get up in the 12th inning of ALCS Game 1 early Sunday morning, he didn't have time to get emotional.

"I'm thinking, 'I'm in,' " said Nix, who replaced Jeter (fractured left ankle) at shortstop and probably will start at shortstop in Sunday afternoon's ALCS Game 2.

"I don't think it has to be said I'm not going to replace him," Nix said. "But the bottom line is somebody's got to step up and we've got to fill that role and move on."

Nix will be joined on the roster by Eduardo Nuñez, who will be activated to replace Jeter. Nix is the more sure-handed shortstop of the two. Manager Joe Girardi said he will make a decision before the game.

"Bottom line, Derek's down and I'm in, so that's an opportunity for me," Nix said. "It's time to do what I can do and I'm excited for it . . . I know I can do things to help this team. We're not done yet. I'm excited for the opportunity and just do what I can to make the most of it."

Nix, 30, started Game 4 of the ALDS at shortstop with Jeter as the designated hitter. Nix went 2-for-3 with a double before getting replaced by a pinch hitter.

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He played in 74 games in the regular season, batting .243 with four home runs and 18 RBIs.

Nuñez was on the roster for the first round and went 1-for-5.

Jeter batted .364 (8-for-22) in the ALDS and was 1-for-5 with a walk in ALCS Game 1.