HOUSTON (AP) The Texans knocked off undefeated Cincinnati and are now tied for first in the AFC South.
Coach Bill O'Brien said that Hoyer was in the league's concussion protocol.
''We're hoping that he'll be able to play for us, but right now it's day to day,'' O'Brien said.
Hoyer was injured on a sack by Domata Peko on the third play of the second half. He did not lose consciousness and got to his feet quickly after the hit that drove his head into the ground. Hoyer remained in the game for the rest of the series, a span of five plays, before heading to the locker room.
O'Brien said it was offensive coordinator George Godsey who first noticed there was something wrong with Hoyer.
''He wasn't functioning correctly as to how we know he would usually function calling a play, receiving the play in, trying to communicate it to the offense,'' O'Brien said.
''So George pointed it out to me when the series was over. I went over to him and he just said: `Look I'm having trouble remembering the plays right now.' So that's kind of where it was at. That's when I ... put my ... stethoscope away and called the trainer.''
T.J. Yates took over after Hoyer was injured and his touchdown pass to DeAndre Hopkins was the difference in the game and the only touchdown of the night. Yates signed with Houston on Oct. 28 to replace Ryan Mallett, who was released after missing the team charter to Miami earlier in the season.
''That's a tough situation for a guy to go into, so one of the things that impressed me and really has always impressed me about him is his demeanor,'' O'Brien said. ''He's a very calm guy, nothing really fazes him.''
Yates was released by the Falcons on Sept. 4 and had been in Atlanta spending his days looking for receivers to throw to, working out and waiting for another chance when Houston picked him up.
When Yates entered the game in the third quarter on Monday night, it was the first time he'd appeared in a game since Sept. 18, 2014, with Atlanta.
But he had history with the Bengals after injuries forced him into the starting role as a rookie with the Texans in 2011 and he led them to their first-ever playoff win with a 31-10 victory over Cincinnati.
O'Brien said Yates didn't get a lot of snaps in practice last week, but had enough to ''go in and function'' He finished 5 of 11 for 69 yards. Despite his rust after not playing for so long, Yates was helped by the rapport he has with teammates from his previous stint in Houston.
''The locker room has a lot of respect for him,'' O'Brien said. ''A lot of these guys have played with him. As soon as he entered the huddle there was already that amount of respect for him and they knew that he would go in there and do his job.''
Hoyer and Yates are the only quarterbacks on Houston's roster, but O'Brien said they have no plans to add a signal caller this week.
The quarterback situation isn't Houston's only concern on offense. They also have to figure out a way to get their running game going. The Texans are averaging just 87.2 yards rushing this season, which ranks 28th in the league. They haven't been great in this area all season, but things have gone downhill since Arian Foster was lost for the season with an Achilles tendon injury on Oct. 25.
Alfred Blue has started the two games since Foster was injured, but has managed just 61 yards rushing in those games combined. Chris Polk and Jonathan Grimes have also received carries with Foster out, and O'Brien was impressed with Polk's work against the Bengals.
Polk had just four carries against Cincinnati, but had a key 13-yard gain, where he barreled over a couple of defenders, on Houston's touchdown drive.
NOTES: O'Brien expects outside linebacker Jadeveon Clowney to return this week after he sat out on Monday night with a lower back injury.
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