"I do want to say that this guy has worked extremely hard to recover from injuries," O'Brien said Monday, per the Houston Chronicle. "And I want to be real clear with this (about) him, as it relates to us here, to the Houston Texans: We think very highly of him. We know that he's going to be a really good player. And he's been unlucky.
"I don't really care about what anybody thinks about what I say in that realm of being unlucky or lucky. I'm just telling you he's had a sports hernia, he's had a concussion and now he's dealing with a knee injury and those things are not easy in your rookie year. And he's in there every day working extremely hard to get better."
O'Brien added that the No. 1 overall pick is day to day and could miss this Sunday's game against the Jacksonville Jaguars with the lingering knee injury.
UPDATE:John McClain of the Chronicle reported Tuesday that Clowney will get a second opinion on his injured knee from Dr. James Andrews on Wednesday.