Houston Texans rookie outside linebacker Jadeveon Clowney had microfracture knee surgery on Monday and is expected to be sidelined for nine months, multiple media outlets reported Tuesday.

The hope is that Clowney will be ready to return for the start of the 2015 season, but there is no guarantee he will be completely recovered by then.

After meeting with orthopedic surgeon Dr. James Andrews last Wednesday, Clowney opted to have the microfracture surgery, which was the second operation on his right knee this year.

The previous surgery, performed in September, repaired cartilage and lateral meniscus damage, according to the Houston Chronicle. Texans general manager Rick Smith told the Chronicle that the team knew microfracture surgery might be required.

Clowney, the No. 1 overall pick in the 2014 NFL Draft, was limited to just four games this season because of health issues.

“This guy’s been injured and it’s time to clean it up and get him back to feeling good and get him back on the field as soon as we can,” Texans coach Bill O’Brien said last week, according to ESPN.com. “He wants to play football. He wants to be good so I think he was disappointed right off the bat. But I think he understands what he has to do and why this is necessary and he knows that he has to rehab hard and get back out there.”

Clowney had sports hernia surgery in June, and he suffered a concussion in August.

He was ready for the start of the season but tore the meniscus in his right knee in the first half of the Texans’ opener and had arthroscopic knee surgery the next day.