All-Pro left tackle Duane Brown suffered a season-ending injury in first quarter of Sunday's 30-6 win over Jacksonville.
"Duane Brown obviously suffered a bad quad injury," O'Brien said Monday. "He'll undergo surgery on Wednesday. Just a little bit about Duane, from the day I arrived here, Duane has been one of the leaders of this football team, one of the best left tackles in football, always out there at practice, always in early, staying late, meeting extra, working in the weight room, doing everything that you would want a leader to do. We're going to miss him, next guy is going to have to step up, but I just want to tell you my feelings on Duane."
Brown, an eight-year veteran, is the longest-tenured Texan earning second place on the franchise's all-time games started list. O'Brien spoke with Brown after Sunday's game and the role he can play moving forward as the Texan begin their postseason.
"He told me he loved me and he appreciated everything that I have done," Brown said. "You know, I am still on this team, I am still a part of this team, mentally, spiritually, so I will still be able to give my leadership abilities even if I am not out there."
Brown was named to two Pro Bowls (2013-14) and as a Pro Bowl alternate this season.
"Duane's a guy that works extremely hard for our team," J.J. Watt said Sunday. "He's a leader on the offensive line. He's been in this organization for a very long time. It's such a terrible feeling to see a guy like that go down because you know how hard he works, you know how much it means to him. It's kind of a chance for us to rally around him. And you know go out there and say, 'Let's win this one for Duane. Let's go out there and make sure we make him proud because we know how badly he wishes to be out there with us.'"
Duane Brown worked with kids at a recent United Way event.