INDIANAPOLIS -- The Colts have gone from feeling good that quarterback Andrew Luck would be ready for the start of the regular season to now not being able to say for sure he'll play Sept. 8 at the Los Angeles Chargers in Week 1.

"We're 3½ weeks away from the regular season, I'm not ready to say," Colts general manager Chris Ballard said Tuesday night regarding whether Luck will play against the Chargers.

Tests done on Luck on Monday night revealed the quarterback has gone from dealing with a calf strain, which he originally was diagnosed with in March, to currently having pain in the "high anklish" area of his left leg.

"From the start we've been dealing with a calf injury," Ballard said. "In March through camp, dealing with a calf and then little area below his calf, which Andrew kind of referred to as a lower leg where he was dealing with some pain, almost in the ankle area. The injury wasn't getting better and hadn't been practicing, so in the course of dealing with the calf injury, it appears that now we have an ankle issue."

Ballard did say that at this point Luck would not play in the preseason. The team's preference is for Luck to strictly focus on rehabbing. There hasn't been any talk of possible surgery for Luck. He has practiced only three days on a limited basis in training camp because of the pain in his ankle area. Luck also missed all of the team's OTA and minicamp practices in the spring.

"There's enough pain where he's not practicing," Ballard said. "That's what we have to get under control. Once we get that under control, I think we can really move forward. There's no question he had a calf [injury]. But the lower part is more of an ankle issue. We get that under control, we can help with the pain."

Ballard said he believes Luck can play at less than 100 percent if necessary this season.

"If he can function, yes," Ballard said. "If his pain is under control and he can protect himself and play good, yes."

The Colts announced July 30 that Luck was going to stop practicing until he felt his calf was 100 percent healthy. Luck said the following day that his Achilles tendon was not at extra risk of injury.

"The issue right now is the side-to-side stuff," Ballard said. "Kind of rolling of the ankle. Anything back-and-forth, he's good. Standing there throwing, he's good. Moving in the pocket, those are the kind of things we have to get him better at."

Ballard said he believes Luck's ankle problem is an accumulation of years of wear on it.

"We think we found it," Ballard said. "Is there 100 percent guarantee? No, but we think we have [found it]. We'll rehab it the way we think we need to rehab it."

Luck and the Colts know he needs some practice time to be ready for the regular season. Ballard said there would be a point when they would have to make a decision on Luck's status against the Chargers.

Backup quarterback Jacoby Brissett, who started 15 games in 2017 for the injured Luck, has been working with the first team in Luck's absence.

Injuries have derailed what was a promising start to Luck's NFL career. He led the Colts to the playoffs in each of his first three seasons, including the AFC Championship Game in 2014, before a shoulder injury in Week 3 of the 2015 season was the start of numerous setbacks for Luck. Since that season, he has missed 26 games, including the entire 2017 season because of shoulder, kidney and rib problems. The Colts went 4-12 in 2017 when Luck was out.

Luck passed for 4,593 yards and 39 touchdowns last season and was named the NFL's Comeback Player of the Year.

"This is not 2017," Ballard said. "When I first came in the door, one of things we talked about was building a team and it wasn't about one guy. Look, I understand the importance of Andrew Luck. He's one of the top five quarterbacks in the league. But we also have another quarterback that we like in Jacoby Brissett. To me, that's part of building a team. You have to be able to handle when things don't go the way you plan them out to be."