ENGLEWOOD, Colo. -- As if the Denver Broncos didn't leave Seattle with enough disappointment packed in their luggage, safety Justin Simmons suffered a thigh injury in the Week 1 loss that will keep him out at least a month.

Simmons, who played every defensive snap Monday night in the Broncos' 17-16 loss to the Seahawks, was formally moved to injured reserve Wednesday afternoon. It means Simmons, who has been the Broncos' iron man, will miss at least the next four games.

The soonest he could return would be for the Oct. 16 game against the Los Angeles Chargers.

The Broncos promoted cornerback Essang Bassey to fill Simmons' spot on the roster and also signed former Minnesota Vikings and Philadelphia Eagles safety Anthony Harris to the practice squad. Bassey, 24, has played in 13 games over last two seasons with the Broncos, while the 30-year-old Harris has played in 95 career games.

Simmons is one of the team captains and has been named to the Pro Bowl once as well as being named a second-team All Pro twice in his career.

Though the Broncos had already decided to move Simmons to injured reserve and signed Harris, coach Nathaniel Hackett would only say Simmons was "going to miss some time'' before Wednesday's practice.

Asked directly if Simmons would be out Sunday against the Houston Texans, Hackett said: "We're still evaluating everything, getting a feel for what's going to happen ... but we're assuming he's going to miss some time.''

Simmons, 28, has started the last 66 games, including Monday's season opener, and had a stretch from the start of the 2018 season until the fourth quarter of the Broncos' Week 3 win over the New York Jets last season when he played every snap -- more than 3,211 consecutive snaps in all.

Those three snaps he didn't play in the 26-0 win over the Jets and the two snaps he didn't play on Dec. 26 against the Las Vegas Raiders were the only defensive plays he had missed since the start of the 2018 season.

He missed the last three games of the 2017 season with an ankle injury.

Against the Seahawks, Simmons finished with nine tackles and recovered a fumble. He did not appear to be limping as he left the field Monday night, but had expressed some discomfort with the injury to the team's medical staff on Tuesday.

"It's hard to replace a guy like Justin Simmons,'' safety Kareem Jackson said. "What he does in our defense, what he does in our locker room with his leadership. It's tough.''

Caden Sterns, who was a fifth-round pick in the 2021 draft, would be the most likely candidate to replace Simmons in the Broncos' lineup.

"Caden Sterns [has] played a ton of ball in this league. ... He's very ready for the situation, ready for the opportunity,'' Jackson said.