The cutting-edge ankle surgery he received was designed in part to speed up his recovery from a sprained right ankle. Tagovailoa had the same surgery last year on his other ankle and returned three weeks later with an outstanding playoff semifinal performance over Oklahoma.

Even before his recent surgery, Tagovailoa told teammates that he would be back against Louisiana State, a battle between unbeaten teams, the winner all but assuring itself one of the four College Football Playoff spots.

Indeed he returned, though Tagovailoa shied away from running with the ball and played with a slight limp as the game wore on. And the limited practiced seemed to show: He lost a fumble, threw an interception and couldn’t bring Alabama all the way back in a 46-41 loss.

Afterward, Saban called him a warrior.

A similar scenario played out this week. Backup Mac Jones got most of the work in practice, and leading up to game time there was uncertainty over whether Tagovailoa would start. But there he was in the lineup, and by the time he was injured, just before halftime, he had Alabama well ahead.

Saban, who said he largely left the decision to play against L.S.U. up to Tagovailoa, called Saturday’s injury a freak occurrence and said Tagovailoa moved well in a pregame workout, perhaps better than he had the week before.

“We can second-guess ourselves all we want,” Saban said.

There will be plenty of that. Saban can earn $800,000 in bonuses if Alabama wins the national championship. There is no such incentive for Tagovailoa. Or any of college football’s stars. Ohio State defensive lineman Nick Bosa had abdominal surgery in September 2018 and prepared for the draft rather than try to return to the Buckeyes. Other players who are top N.F.L. prospects now routinely skip bowl games that are not part of the playoff.