Jadeveon Clowney had sports hernia surgery Thursday and will miss next week's mandatory three-day mini-camp, Houston Texans coach Bill O'Brien told reporters Friday.

Clowney, the No. 1 overall pick in the NFL Draft, raised eyebrows when he unexpectedly missed practice Thursday in Houston. The reason was an excusable one, but still a tough blow for a rookie making a challenging adjustment from defensive end to outside linebacker.

The former South Carolina star is expected to return by the start of training camp in August, according to reports. Still, he'll miss three important days next week.

O'Brien told reporters the injury hadn't been bothering Clowney for long. Clowney and the team decided to have surgery now before it got any worse.

"It was the best thing for J.D. and the best thing for our team and the best thing for our organization," O'Brien told the Houston Chronicle. "He'll be ready to go for training camp. That's about all I'll say about that."

Clowney had several nagging injuries in his final season with the Gamecocks, most notably bone spurs in his right foot. He also missed South Carolina's game against Kentucky last October with a strained muscle near his ribs, and he had a groin injury during his pro day at Williams-Brice Stadium in April.

Earlier last season, Clowney said he expected to have foot surgery to repair the bone spurs. He later said no surgery would be required.

Clowney signed a four-year rookie contract earlier this month worth more than $22 million, with more than $14 million as a signing bonus. Before his surgery, he had been impressing coaches with his work ethic and commitment to learning the playbook.