Thompson, the Redskins' most dynamic player this season, suffered the injury at the end of a third-down run by quarterback Kirk Cousins. Thompson was engaged in a block, and his right leg bent back after he got caught in an awkward position under Saints defensive tackle Sheldon Rankins.
An air cast was placed on Thompson's right leg before he was helped off the field and loaded onto the cart. Teammates gathered around him and offered words of encouragement as he was lifted up.
Cousins also took a heavy hit on the play and received brief treatment from trainers while Washington executed a successful fake punt on fourth-and-1 on its own 15. Cousins came back on the field and led the Redskins on a touchdown drive, hitting Ryan Grant on a 40-yard scoring pass for a 24-13 lead.
The lead didn't last, however, as the Saints rallied to tie the game at 31-31 in regulation thanks to Alvin Kamara's 18-yard touchdown reception and two-point conversion rush with 1 minute, 5 seconds remaining, then won 34-31 in overtime when Wil Lutz kicked a 28-yard field goal.
"That hurts me more than anything, that we lost for Chris," Redskins safety D.J. Swearinger said. "I told him we'll bring this back home for him. I didn't keep my word. If anything bothers me, that bothers me the most. We have one of our best guys go down, and we didn't get the W for him. That's tough. That's tough."
Thompson tweeted about his injury after the game, writing: "This hurts."
This hurts. Not being able to go out and perform for my God who blessed me with this ability, my brothers, coaches, and the fans. But if you know me you know I'm gonna work my butt off to be out there for y'all next season even better than I️ was before. Thanks for the support.
— Chris Thompson (@ChrisThompson_4) November 19, 2017
Thompson entered the game leading Washington in rushing (277 yards) and receiving (494) and had scored four touchdowns. He also has improved dramatically in pass protection the past two years.
"He's one of the most important players on our offense, especially when you get the ball back and need him for pass protection routes coming out of the backfield there at the end," Redskins coach Jay Gruden said. "We obviously have to make do with the guys we have, and we will."
The Redskins already lost running back Rob Kelley for the season with an ankle injury. They now have two running backs on the active roster: rookie Samaje Perine and Byron Marshall, signed earlier in the week off the Philadelphia Eagles' practice squad.
The Redskins have suffered a number of injuries this season, but Thompson's could arguably be the biggest because of his productivity and the fact that he'll be difficult to replace. Marshall offers quickness and played some receiver in college, but Thompson's ability to pass protect has made him invaluable.
"To have him go down is a huge, huge setback for us," tight end Vernon Davis said. "Chris Thompson is one of the best in the league when it comes to running the ball, catching and making plays. To lose him is tough. It's hard to replace a guy like that with his talent and his ability to do what he does. It's a tough situation to be in."
Redskins offensive tackle Morgan Moses echoed this sentiment.
"It's hard to replace a guy like that," Moses said. "You might not be able to replace a guy like that, what he brings to the offense, what he brings to the locker room. ... But we can't [dwell] on it."
The Associated Press contributed to this report.