WESTFIELD, Ind. — Indianapolis Colts general manager Chris Ballard on Tuesday night said recent tests have revealed that quarterback Andrew Luck, who has been dealing with pain in his calf, has an injury to the front of the ankle, and will likely sit out the preseason.

In a conference call with local reporters, Ballard wanted to clarify that Luck was not found to have injured his os trigonum, a small bone located behind the ankle, which at one time was believed to be a possibility. And while tests show the quarterback does indeed have a strained calf, the team believes it has isolated the issue to the front of his left ankle, which has caused pain in the area for months.

Ballard did not provide an immediate timetable for Luck's expected return, but is hoping that a change in his rehab to address the front of the ankle can provide a viable solution by the time he would need to begin preparing for the team's Week 1 game against the Los Angeles Chargers.

That game on Sept. 8 is about 3 1/2 weeks away.

"Once we get that under control then we can really move forward," Ballard said. "All players need reps and he knows that, and he knows he needs to get out there and get his reps. So we'll play that kind of day-by-day."

Ballard expressed confidence in his team and backup quarterback Jacoby Brissett should it need him to take over until Luck is able to get back. Brissett has taken all the first-team reps in on-field workouts and practices since the start of the offseason workout program through this point of training camp and the preseason.

"I think we've got a pretty good football team — we're young, but we've got a pretty good football team," Ballard said. "We like Jacoby Brissett, also. And I trust Andrew and I know he's going to do everything in his power to get back.