Brian Cushing suffered a sprained MCL in Sunday's 24-13 win over the Chicago Bears and will not play in Week 2.
"Brian will be back, I would say, sooner rather than later," O'Brien said. "He's a guy that's obviously played a long time. He knows exactly what's wrong and he'll work very hard to get back as quickly as he can."
O'Brien did not elaborate on Cushing's expected return date, but did say he would be "out for a bit." The veteran linebacker's presence will still be felt around the locker room as the Texans prepare to face the Kansas City Chiefs in Week 2.
"Brian Cushing, who's out, has already told me that he's going to be around all week," O'Brien said.
Cushing exited the game after the first defensive series and did not return. Second-year linebacker Max Bullough finished the game with a career-high five solo tackles, including one for a loss.
Duane Brown will also miss the Week 2 matchup against the Chiefs, per O'Brien. The starting left tackle has been working his way back from his January quadriceps surgery. Brown spent the entire preseason on the Active/Physically Unable to Perform List, but was moved to the active roster on Sept. 3.
The (1-0) Texans will host the (1-0) Chiefs on Sunday with kickoff set for noon CT.
Check out the best photos throughout the Texans first regular season game vs. the Bears.