Dave Martinez will not manage the Nationals in St. Louis on Monday because he stayed in Washington to undergo a heart procedure.

Nationals general manager Mike Rizzo told the media that Martinez experienced chest pains during the team's home game against Atlanta on Sunday. The manager left in the sixth inning and was taken to a hospital.

Martinez, 54, underwent a cardiac catheterization and will remain in the hospital undergoing tests. Rizzo said that Martinez was "upbeat" but that there was no timetable for his return.

Bench coach Chip Hale will manage the team Monday. He replaced Martinez on Sunday.

The Nationals currently own the first wild-card spot, 1.5 games ahead of the Chicago Cubs. This is a key three-game series against the NL Central-leading Cardinals.

Martinez is in his second season managing the Nationals. After winning 82 games last season, the Nats have matched that total this season with 14 games to play.

Martinez had a 16-year MLB career with nine teams.