Team officials had feared after Sunday's game that he had torn his Achilles and would miss the season; an MRI confirmed those fears Monday. Collins told NFL reporter Josina Anderson about the surgery date.
Collins was placed on injured reserve Tuesday. Washington signed safety Jeremy Reaves from the practice squad in a corresponding move.
Washington is considering all options in replacing Collins, although veteran Eric Reid told The Associated Press on Tuesday that he declined an offer from the team to join its practice squad.
Collins tore his Achilles in the second quarter of Sunday's 25-3 win over the Dallas Cowboys. He was having his best game of the season, having recorded a sack/fumble that led to a safety in the first quarter and finishing with four tackles and another quarterback hurry.
"It's always tough when you lose a good football player," Washington defensive coordinator Jack Del Rio said. "He's a tough guy that was voted a team captain by his peers. Obviously, anytime [an injury] happens, it's something you have to work to overcome. We're just going to ask him to heal up and stay positive. We're going to carry on. We're going to continue on and expect to play well."
Del Rio said he texted with Collins after the game Sunday.
"I encouraged him to keep his head up, keep his spirits high and heal up and obviously that we'd miss him," he said. "Love and respect to him. Heal up. We're going to carry on."
Collins will be replaced by rookie Kam Curl in the immediate future. Deshazor Everett, who can play both safety spots, will stay at free safety. Washington can also use former starting free safety Troy Apke in various packages and corner Kendall Fuller at safety in obvious passing situations.
"You lose a great player, great leadership in the locker room," Washington defensive tackle Jonathan Allen said. "You lose a lot with Landon."