Just about everyone in Waco, Texas assumed Isaiah Austin had played his last game in a Baylor uniform. And until last week, they were probably correct.

Austin, a 7-foot-1 center, was projected as a mid-to-late first-round pick in this summer’s NBA draft and had given no indication to his coaches or teammates that he would return to school. Things changed Sunday, though, when Austin announced he’d be back for his sophomore season.

So what happened?

A source told ESPN.com Sunday that an MRI performed late last week revealed Austin had torn the posterior labrum in one of his shoulders. The source said the injury would have prevented Austin from going through individual workouts with NBA teams during the next few months.

Austin’s shoulder issues wouldn’t have been as big of a deal if he were tabbed as a top-10 pick. But because he was projected to go in the early-to-mid 20s, Austin needed the workouts to make a positive impression on teams and solidify his status as a first-rounder. First-round picks receive guaranteed three-year contracts. Second-round picks are promised nothing.

Austin didn’t want to risk it.

“Today might have literally been the worst day of my life,” Austin tweeted Friday, the same day he is said to have received the MRI results. “Actually, it is the worst day.”

Baylor coach Scott Drew -- reached on his cell phone shortly after meeting with Austin at his Arlington, Texas home late Sunday night -- was skeptical to talk about the specifics of Austin’s injury because of privacy laws.

“But I can confirm that he suffered an injury, and that it affected his decision,” Drew said. “He’s been very mature with how he’s handled this.”

Drew said Austin's love for Baylor and his teammates made it easier to come back.

“He still could’ve left school and been drafted,” Drew said. “But he likes it here. He’s enjoyed his time here so far. If he didn’t like his teammates and if he didn’t like Baylor he wouldn’t have come back. I think that says a lot.”

Austin’s return is a huge boost for Baylor and will likely vault the Bears into the Big 12 title discussion along with Oklahoma State and Kansas. The Jayhawks have won nine straight conference crowns but lose all five starters from last season’s 31-6 team.

Baylor’s frontcourt of Austin, Cory Jefferson (who also considered entering the draft) and Ricardo Gathers will be among the best in the country. The trio combined to average 32 points and 22 rebounds for a team that went 23-14 last season and won the NIT championship.

Point guard Pierre Jackson -- last year’s Big 12 scoring and assists leader -- is gone and will be almost impossible to replace on the perimeter. But the Bears are hopeful that either rising sophomore L.J. Rose or junior college signee Kenny Cherry can step in and fill the void.

Brady Heslip and Gary Franklin are seniors who will both see extended minutes at shooting guard. And incoming freshman Ishmail Wainwright, who stands 6-foot-6, will give Baylor the long, athletic small forward it so glaringly lacked last season following the departure of Quincy Miller.

Baylor is also in the mix for a handful of potential transfers that could impact its team immediately.

No player on the roster, though, will boast as much talent as Austin, who averaged 13 points and a team-high 8.6 rebounds as a freshman. Once Austin regains his health -- it hasn’t been determined whether surgery will be needed to repair the torn labrum -- Baylor coaches want him to focus on gaining size and strength.

One of the biggest knocks on Austin is that’s he’s too skinny and not physical enough, which made him a huge liability on the defensive end of the floor at times last season, when he played at about 210 pounds. Drew said he’d like to see Austin at about 225 or 230.

“He needs to gain weight, gain strength,” Drew said. “Just like most every freshman, he hit a wall late in the season. Weight training allows you to go through that wall. That’s why strength and conditioning is so important.”

Austin also displayed bouts of immaturity at times, whether it was poor body language on the court or not doing the right things at practice.

“We talked about those things when I met with him tonight,” Drew said. “But he was already getting better in those areas. He matured during the season and it was really noticeable in the end. His focus is on getting better, just like it will be for all of us.”