HOUSTON — The Houston Texans placed star defensive end J.J. Watt on injured reserve Wednesday and his return this season is in doubt.

Coach Bill O'Brien said Watt had re-injured his back and putting him on IR was the best thing for his long-term health. The team was still exploring the injury and it's unclear if it will require surgery. Watt is not expected back before December, if at all.

Watt, who has won Defensive Player of the Year for the past two seasons, missed training camp and Houston's four preseason games after surgery in July to repair a herniated disk in his back. He started each of the team's three regular-season games and got hurt again Thursday against the Patriots.

Watt tweeted a statement that did not provide details on his injury. It began with: "Adversity sucks. Your attitude towards it doesn't have to. I will be back."

"This won't be fun, but it is necessary in order for me to return to 100 per cent and play at the level that I am capable of playing at," the post said. "Everybody deals with adversity in their lives, many much worse than what I'm going through. I have great people around me and I appreciate the thoughts and well wishes from all of you. I am looking forward to the fight back to the top and to the next time that I can step back on that field with my brothers to play the game that I love."

It's a major blow for Houston, which selected Watt with the 11th overall pick in the 2011 draft. Watt has played 83 consecutive games for the Texans despite various injuries, including torn core muscles and a broken hand last season.

This was a tough off-season for Watt, who had surgery in January to repair five torn core muscles before going under the knife again in July to repair his back.

Watt, who led the NFL with 17 1/2 sacks last season, has 1 1/2 sacks this season to give him 76 for his career.

The 27-year-old is a three-time Defensive Player of the Year and a four-time Pro Bowler. He's been a force since entering the league not only because of his pass-rushing prowess, but also because of his uncanny ability to swat down passes. He has 45 passes defended in his six-year career. He has forced 15 fumbles and recovered 13.

The Texans signed veteran defensive end Antonio Smith to take his spot on the roster.