"That decision may be made before training camp," O'Brien said. "They're out here competing (in OTAs and at mandatory minicamp) every single day, and it's pretty intense. So, we may pick a guy very soon. And if we don't, and the decision does go into training camp, it'll be made pretty early on. The team needs to know who the guy is, and we need to go forward."
Mallett appeared in three games for Houston in 2014, throwing for 400 yards, two touchdowns and two interceptions with a 54.7 completion percentage.
Hoyer played 14 games for the Browns last season, completing 55.3% of his passes for 3,326 yards, 12 touchdowns and 13 interceptions.
The Texans, who finished 9-7 in 2014 and narrowly missed the playoffs, will be featured on HBO's "Hard Knocks" during training camp.
- Alex Putterman