Surgery was the best option to repair a herniated disk rather than rehab and rest, according to multiple reports.
Watt, a three-time winner of the NFL Defensive Player of the Year Award, was placed on injured reserve Wednesday. He saw a specialist and elected to have the surgery, according to John McClain of the Houston Chronicle.
Watt underwent back surgery on the same disk in late July and sat out the preseason. He returned to play each of the Texans' first three regular-season games, but observers wondered if he was actually healthy.
Under league rules, Watt could play in eight weeks but the Texans reportedly don't want to take any chances with his health this season.
Watt posted on social media Wednesday that the IR move was "necessary in order for me to return to 100 percent and play at the level that I am capable of playing at. Everybody deals with adversity in their lives, many much worse than what I'm going through. ... I look 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 before the best fans in the world and I promise to continue to do everything in my power to make you proud."
The Texans agreed to a deal with defensive end Antonio Smith on Wednesday. Smith has played for the Texans and is familiar with defensive coordinator Romeo Crennel's scheme.
The Texans' fifth-ranked defense features talented pass rushers with speed and power like Whitney Mercilus and Jadeveon Clowney and stout run-stoppers in inside linebackers Brian Cushing and Benardrick McKinney along with nose tackle Vince Wilfork. However, no individual player comes close to approaching Watt's unique skillset as an athletic 6-foot-5, 290-pounder capable of routinely bull-rushing through blockers or defeating them with his superior speed.
Watt, 27, managed only eight tackles and 1.5 sacks through three weeks this season. It was a significant drop-off from last season, when he recorded 17.5 sacks and three forced fumbles en route to his third Defensive Player of the Year honor. He also captured the award in 2012 and 2014, finishing with 20.5 sacks and four forced fumbles each year.
Watt, Houston's 2011 first-round pick (11th overall) out of Wisconsin, has 76 sacks, 15 forced fumbles and one interception in 83 games, all starts. He has never missed a regular-season game.