"Any time they operate, it's probably a couple months anyway, if not the whole year," Washington manager Davey Johnson said. "He's going to be hard to replace."
Tracy was placed on the 15-day disabled list Monday and traveled to Philadelphia for a Tuesday MRI after he sustained the injury while running to second on a pinch-hit double during the Nationals' 8-4 win against the Braves on Saturday.
In 32 games this season, Tracy hit .265 with a .327 on-base percentage while serving as Johnson's go-to left-handed hitter in late-inning situations, a role that could now fall on Corey Brown, who earned his first career start Tuesday against the Marlins.
The injury to Tracy is just the latest in a long line of ailments to sideline Nationals players, as the team now has 14 players on the DL.
"I've never seen anything like it, and I'm kind of a dinosaur," Johnson said. "I've never had a club that had so many key players go down."