"We haven't really seen him since the end of the season, so I really don't know," O'Brien told reporters at Texans training camp. "I can do my best to answer your question, but, really don't know."
Clowney, who hasn't inked his franchise tender, has stayed away from all team activities throughout the offseason. Since he isn't signed, the 2014 first overall pick can't be fined.
"When he arrives, we'll handle it when he arrives," O'Brien added. "That's his prerogative, he doesn't have to be here right now. That's part of the franchise tag and all those different things."
Clowney is seeking a long-term extension, but the Texans don't seem motivated to give him one. Reports earlier in the offseason suggested O'Brien wasn't as enthusiastic about giving Clowney a lucrative deal as former general manager Brian Gaine.
Clowney has been extremely productive over the last three seasons while recording 24.5 sacks, but his checkered injury history could be a stumbling block in negotiations. He's battled knee problems throughout his career.
Barring an extension or trade, the 26-year-old is expected to sign his tag and report to the Texans at the end of the preseason.
"At some point he'll come in, I believe," said O'Brien. "But that's up to him."