Mercer didn't participate in Monday's practice session due to an upper-body injury, Mitchell Clinton of the Jets' official site reports.
Mercer hasn't yet been ruled out for Tuesday's game against Montreal, but a better idea of his status could come into focus based on whether he participates in Tuesday's morning skate. The 25-year-old has appeared in each of the Jets' first 15 games of the regular season, recording six assists, 13 hits and 10 blocked shots while averaging 15:24 of ice time.