Locker also injured the same shoulder in the Titans' Week 1 loss to the Patriots. The coach said Locker's injury is "similar to last time" and the team will know more about the quarterback's status Tuesday or Wednesday.
"The MRI was very similar," Munchak said. "It popped out, and they popped it back in. He's real sore right now, so they're just waiting a couple of days to get a full examination."
A league source told ESPN NFL Insider Adam Schefter that, due to a separated left shoulder, Locker is not expected to play Sunday at Minnesota.
Locker injured his left shoulder after being sacked by the Houston Texans in the first quarter on Sunday, and missed the rest of the game.
He returned to the sideline in the second quarter in street clothes with his left arm in a sling.
Locker was sacked by Glover Quin and thrown to the ground. He remained there for a few minutes in pain while trainers attended to him. He eventually got up and walked off the field before being taken to the locker room.
Quin was uncovered at the line, something Locker didn't notice until it was too late.
Matt Hasselbeck came in for Locker and completed 17 of 25 passes for 193 yards and two touchdowns. He also threw two interceptions that were both returned for Houston touchdowns.
Munchak said Locker surprised everyone by how quickly he recovered when he hurt the shoulder before. But the coach also says Locker held the ball too long on a three-step drop and must throw quicker.
Munchak said the Titans won't necessarily rest Locker just to give the shoulder time to heal to prevent him from another dislocation.
"Obviously, rest is better than playing football with any injury. Not playing football would be good for all of us, but I don't know that he would sit out for that reason," Munchak said.
Defensive tackle Jurrell Casey played in college at UCLA against Locker when the quarterback was at Washington. He's seen up close how Locker kept playing no matter how many times defenses hit him.
"I have no doubt he's going to come back strong, and he's going to lead us as he's been leading us," Casey said.
Information from The Associated Press was used in this report.