HOUSTON -- The Texans said Friday that rookie quarterback C.J. Stroud is doubtful for Sunday's game against the Tennessee Titans.

Coach DeMeco Ryans said Stroud is "feeling better but still is in the concussion protocol" as he hasn't practiced with the team this week.

Stroud suffered a concussion when New York Jets defensive tackle Quinnen Williams delivered a blow in the fourth quarter of Sunday's 30-6 loss that knocked him out of the game.

Quarterbacks Davis Mills or Case Keenum could start in place of Stroud, who has started all 13 games for the Texans this year. Keenum hasn't dressed in any game this season, as he's been the emergency quarterback. In situations where Stroud briefly left the game this year, Mills stepped in.

But throughout this practice week, the Texans have split reps with Mills and Keenum, sources told ESPN.

When Ryans was asked if Mills would start, he didn't directly answer.

"Both guys have prepared this all week, just like every position, everybody's prepared," Ryans said on Friday. "I told everybody on Wednesday everybody needs to prepare as a starter, that's how we approach it...Both guys have done a great job with everything that we've asked the guys to do. They've done a great job running the show. We had a really good week of practice."

Mills went 5-20-1 as a starter in his first two seasons in Houston, throwing for 5,802 yards with 33 touchdowns and 25 interceptions.

"With time come reps and experience," Mills said on Thursday. "I think just the amount of opportunity I've had and the experience I've been able to build over these past couple of years has made me a better player. I'm looking forward to it."

Keenum, 35, hasn't started since 2021 when he replaced Cleveland Browns quarterback Baker Mayfield for two games. Keenum went 2-0 in that stretch and threw three touchdowns with one interception.

For Keenum's career, he's 29-35 as a starter and has thrown 78 touchdowns and 48 interceptions. He has played for seven different franchises -- the Texans, Rams, Vikings, Broncos, Commanders, Browns and Bills.

Whoever starts will receive some help in the skill player department as tight end Dalton Schultz, who's third on the team in receiving yards (455), will play against the Titans after missing the last two games (hamstring). However, Nico Collins, the team's leading receiver and 11th in receiving yards (1,004), is questionable with a calf injury as Collins hasn't practiced all week.

The potential loss of Stroud could disrupt a potential record-breaking season.

Stroud is second in the NFL in passing yards (3,631) and is 743 yards short of tying the NFL record for passing yards for a rookie held by former Indianapolis Colts quarterback Andrew Luck (4,374). If he returns in Week 16, he would have to average 248 yards per game for the next three games to eclipse Luck's record.

The injury to Stroud comes with the Texans one game behind the Jacksonville Jaguars (8-5) in the AFC South and tied with five other teams at 7-6 at No. 6 in the conference, with only three wild-card spots up for grabs if they can't catch the Jags. ESPN's Football Power Index gives the Texans a 45% chance to make the playoffs coming into Week 14.