Khalil Mack will undergo foot surgery and is out for the season, Akiem Hicks won’t play Sunday and Allen Robinson is doubtful for the Chicago Bears

A tsunami of injury developments crashed down on Halas Hall on Friday. The Chicago Bears must now show how equipped they are to handle this latest flood of adversity with another season slipping away.

Khalil Mack is done for the year, formally placed on injured reserve Friday afternoon and scheduled to undergo left foot surgery next week. That’s the most significant setback for the Bears as they push to snap a four-game losing streak Sunday against the Baltimore Ravens at Soldier Field.

“This is part of the game. You try to handle things the right way,” coach Matt Nagy said. “I know he’s frustrated because he’s such a competitor. But this is the best thing for him and the best situation to be able to help him out and get him fixed.”

Still, Mack’s exit from the 2021 stage is far from the only hardship the Bears have to work through. Defensive lineman Akiem Hicks was declared out for Sunday, still dealing with a nagging groin injury. Receiver Allen Robinson, meanwhile, is doubtful to play with a hamstring issue that kept him out of practice the entire week. And veteran linebacker Danny Trevathan was also moved to IR on Friday with a knee injury.

At 3-6 and without a victory since Week 5, the Bears again will be tested, and their ability to adapt will prove crucial to keeping this season on the rails.

Mack has been dealing with a foot issue since late September, initially playing through pain for four games in October despite minimal practice time. The Bears chose to put him on the shelf in Week 8 against the San Francisco 49ers, hoping additional time off might help matters and allow him to get back on the field.

But after Mack sat out the last two games and then followed with extra down time during the bye week, his foot injury did not show enough improvement. Thus a decision was made for him to have surgery to address the injury.

Nagy was asked Friday for specifics of Mack’s injury and what the procedure next week will be aiming to fix but offered only a vague response that the issue is related to something in one of Mack’s toes.

“That’s for the doctors and all them. That’s not for me,” Nagy said. “I just know this is the decision we’ve made. ... That’s not my profession.”

The Bears signed 34-year-old edge rusher Bruce Irvin to their practice squad Friday and promoted Cassius Marsh to the active roster, moves designed to help compensate for Mack’s absence. But it remains to be seen just how much Irvin can help and how soon, particularly with the Bears having two games and very little practice time in a span of five days.

Irvin is in his 10th season in the league but played only two games for the Seattle Seahawks last season before suffering a torn anterior cruciate ligament in his right knee. That injury ultimately required two surgeries, the most recent in January, and Irvin’s first football practice in 14 months was Friday’s session in Lake Forest.

Nagy said Irvin made a good first impression, initially with a workout Thursday and then during his first day on the job Friday. “I like his energy and I like his mentality,” the coach said.

But Nagy also knows the Bears coaching staff will have to get a quick feel for where Irvin is at mentally and physically. And the only way to gauge that will be on the practice field.

“It’s the only place we can do it,” Nagy said. “He’s going to have to let us know how he feels.”

Mack was off to a promising start this season. He had six sacks in the seven games he played and was a significant factor in the defense’s resurgent pass rush. Now the Bears will march on without him.

“There’s no way you can fill his shoes,” Eddie Goldman said. “But you just try to get to the quarterback as much as you can.”

The Bears also can’t be certain when Hicks might return as he battles his groin issue. The 32-year-old defensive lineman will miss his third game this season and his 15th in the last three years.

Robinson, too, may be out of action, leaving the passing attack to work through contingency plans. The other receivers on the 53-man roster are Darnell Mooney, Marquise Goodwin, Damiere Byrd and return specialist Jakeem Grant. Nagy indicated Friday that Rodney Adams and Isaiah Coulter could be candidates for a weekend promotion to the game-day roster.