Tua Tagovailoa never saw it coming.

And now, the Miami Dolphins aren’t sure when they’ll see their starting quarterback play again.

Tagovailoa was carted off the sideline during the first quarter of Sunday’s game against Buffalo with a rib injury, getting knocked out in the second series. The Dolphins initially said he was questionable to return, then ruled him out, and now will wait to find out what doctors say about his availability going forward.

“We’re getting some tests run,” coach Brian Flores said after the 35-0 loss to the Bills. “Don’t know the severity of the injury right now. We’re going to run some tests tonight and tomorrow morning and hopefully have a little bit more information.”

Tagovailoa was hit by Buffalo’s A.J. Epenesa on the final play of Miami’s second series. The Dolphins went for it on fourth-and-2 from near midfield. Epenesa was completely unblocked as Tagovailoa dropped back and drove Miami’s quarterback to the turf as he threw.

Tagovailoa remained down for a moment, grimacing and grabbing at his left side. He could barely walk — it was more like a slow shuffle — to the sideline. The cart was waiting to take him off the field and to the locker room area for evaluation, and Tagovailoa wasn’t seen again.

Tagovailoa was sacked twice on Miami’s first series, then took the big hit from Epenesa in the next series. Jacoby Brissett came in at quarterback.

“Thinking about him right now,” Brissett said of Tagovailoa. “I don’t want this to sound bad, but it’s part of the game, just being ready to go. My number was called. It wasn’t my first time in this situation.”

Tagovailoa’s diagnosis will determine what Miami does next. Tagovailoa and Brissett are the only quarterbacks on the active roster; Reid Sinnett is on the practice squad if the Dolphins choose to make a roster move.

Or they could look elsewhere.

Speculation has swirled since August, at least, regarding the Dolphins’ interest in embattled Houston Texans quarterback Deshaun Watson, who has been accused of sexual assault and harassment in lawsuits filed by 22 women.

Watson and his lawyers have denied the accusations against him. No charges have been filed.

Flores has not confirmed reports that Miami has been involved in trade talks regarding Watson, but said last month that he wants players of high character.

“There are a lot of things we weigh when we’re making decisions — fit on the team, overall talent, salary cap,” Flores said in August. “When we’re talking about a player or players, we’re always trying to do what is best for the Miami Dolphins. There are a lot of variables. We want a group that is tough, smart, competitive, loves to play and is team first. Those are the types of guys we’re looking for.”

Tagovailoa entered this season nearly two years removed from the hip injury that ended his college career at Alabama. He took over as Miami’s starter midway through last season, his rookie year.

“I’m hopeful that Tua’s back,” Flores said.