Carp, 25, suffered a sprained right shoulder diving for a double hit by Oakland's Kurt Suzuki in the fourth inning of Wednesday's Opening Day victory in the Tokyo Dome. Carp stayed in through the entire 11-inning game, going 0-for-4 but making several running catches later in the game.
Chone Figgins replaced Carp in left field for Thursday's second game against the A's at the Tokyo Dome, with Kyle Seager starting at third base.
Peguero, 25, was already with the team in Japan as part of the 30-man travel roster, but was optioned to Triple-A on Tuesday to get the Mariners to the 28-man limit for the two games in Japan.
Carp will be re-evaluated when the team returns to Peoria, Ariz., on Friday. He was one of the Mariners' breakthrough stories last year when he hit .276 with 12 home runs and 46 RBIs after being called up in midseason. If Carp recovers quickly enough, he would be eligible to return in time for the Mariners' home opener on April 13 against the A's.
Peguero hit .196 in 46 games last year with six home runs and 19 RBIs. The 6-foot-5, 245-pounder has a team-leading four home runs in Cactus League play this spring and has hit .256 in 43 at-bats.