ESPN's Adam Schefter first reported the news on Thursday night.
NFL Network's Ian Rapoport reported the Texans knew Watt's 2016 campaign was finished and that surgery was the best course instead of rest or rehab.
The three-time NFL Defensive Player of the Year reinjured his back during Week 3's game against the New England Patriots. The team placed him on the injured reserve list Wednesday, which ensured he would miss an NFL game for the first time since being drafted 11th overall in 2011.
Shortly after being shelved, Watt vowed he would come back strong:
The 27-year-old faced a harrowing offseason, suffering numerous injuries, but he still made it back onto the field for 2016.
"When I was in Philadelphia after the first surgery, there were some days there where I really, really questioned whether or not I would ever be able to play again," Watt added.
Before that, Watt suffered a broken hand and a groin injury after initially herniating his disk during the middle of 2015, per Wesseling.
Watt underwent his first back surgery to fix the herniated disk in July, when he told Wesseling it was "almost a fun challenge to overcome."
Watt, one of the greatest pass-rushers the game has ever seen thanks to a dominant four-year stretch from 2012 to 2015, is irreplaceable on Houston's defensive line.
In only five full seasons, his 76 career sacks already rank 12th among all active players and 69th in NFL history.
Now the Texans will look to Jadeveon Clowney, John Simon, Whitney Mercilus and Benardrick McKinney to keep the pass rush successful. Those four have combined for 7.5 sacks through three games this season and will have to continue putting up similar numbers if the 2-1 Texans want to remain a threat in the AFC South.
Stats courtesy of Pro-Football-Reference.com.