Exactly one year after tearing his ACL against Arizona, Nick Bosa was supposed to face the Cardinals again. Instead, another injury has interrupted his comeback.

The comeback of Nick Bosa in the NFL has once again taken an unusual turn. The defensive end for the San Francisco 49ers is set to be out for a few weeks due to the injury he suffered in his calf muscles during practice on Thursday, reports Adam Schefter of ESPN and Ian Rapoport of NFL Network.

Bosa won’t be available to play in Sunday’s game against the Arizona Cardinals.

The timing is particularly striking.


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It was nearly one year later that Bosa would be playing against Arizona, since he tore his ACL in his right knee the year before, when playing against the Cardinals. He had come back after rehabbing from his injury last season and started the new season.

Instead of completing a full-circle moment against the team involved in his ACL setback, Bosa will now begin another period of recovery.

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ESPN reported that the five-time Pro Bowl defensive end had played 70 defensive snaps across San Francisco's first two games of the season. The calf injury now adds another complication to his comeback and leaves the 49ers without one of their most important pass rushers.

The problem is occurring during a tough period for the San Francisco defense as other players at the same position have already been ruled out due to injury, making the roster at the position considerably smaller.

Bosa's comeback was building toward Arizona

Bosa's return had been one of the major storylines surrounding the 49ers entering the season.

The defensive end suffered his second career ACL tear against Arizona last season, ending his campaign and beginning another lengthy rehabilitation.

Therefore, he returned this year under some precaution as San Francisco was easing him into their defensive lineup.

In the initial two games, Bosa saw action for 70 plays, as per ESPN, which gave the 49ers a chance to manage his playing minutes following the extended absence.

Week 3 also came with an added dimension: the opponent team, which was Arizona.

It happened that Bosa suffered his ACL injury while playing against the Cardinals nearly a year ago, and therefore, the match against the Cardinals this coming Sunday marked the exact anniversary of his injury.

That plan changed during practice.

Bosa was listed as a nonparticipant Wednesday with a designation related to his knee and described as a resting player.

Calf strain was added to the list of injuries on Thursday, as he missed practice. The calf injury was projected to sideline him for a couple of weeks, according to ESPN reports, noting that on both Wednesday and Thursday, Bosa missed his normal weekly media availability.

The calf injury was treated as a new problem, not as a result of continuing with the recovery from the ACL injury.

A depleted defensive line loses its biggest name

Bosa's absence would be significant under normal circumstances. For the 49ers, it comes after a string of injuries has already thinned the defensive front.

ESPN reported that San Francisco placed defensive tackle C.J. West on injured reserve this week after a knee injury.

Also, the defensive end, Sam Okuayinonu and the defensive tackle, Alfred Collins, have been placed on IR after getting injured in the early weeks.

The rookie defensive tackle, James Thompson Jr., is nursing an ankle injury which will keep him out of action for three to six weeks.

The rookie edge rusher, Romello Height, is suffering from a broken hand.

Coach Kyle Shanahan said Height had an outside chance of playing against Arizona, according to ESPN.

The result is an unusually thin defensive front.

With Bosa unavailable, ESPN identified Keion White, Khalid Kareem and Ogbo Okonkwo among the available defensive ends. Mykel Williams remains on the physically unable to perform list while recovering from a torn ACL suffered last season.

Williams is expected to return to practice next week, but he cannot play until Week 5, when San Francisco visits the Seattle Seahawks, ESPN reported.

That leaves the 49ers needing to get through the Cardinals matchup without several players who were expected to contribute to the defensive rotation.

Why the IR decision matters for San Francisco

The 49ers are not simply deciding how long Bosa might be unavailable. They are also weighing how to manage a roster already under pressure from injuries.

ESPN reported that San Francisco is leaning toward keeping Bosa off injured reserve, partly because the team is concerned about running out of its available IR return opportunities later in the season.

That consideration only makes for a more complex issue.

Having players on injured reserve will be useful as far as flexibility is concerned. However, putting players on injured reserve will affect the time in which they can return. The 49ers will have to make a choice on who gets a return from their list.

Shanahan acknowledged earlier in the week that the team could not simply place every injured player on IR and expect to bring everyone back later.

"There are a lot of variables there," Shanahan said, as reported by ESPN.

For Bosa, the decision will depend partly on the expected recovery period.

If the calf injury keeps him out only for a short stretch, San Francisco could decide that putting him on IR would unnecessarily consume one of its return opportunities. If the recovery takes longer, the roster flexibility provided by an IR designation could become more attractive.

For now, ESPN reports that the 49ers are still working through that decision.

What Bosa's absence means for his comeback

Bosa's return from his ACL injury had already been a story of gradual progress.

He made it through the opening two games and was building his workload after missing the previous season. The expectation was that his role would continue to grow as he became more comfortable following the long rehabilitation.

The calf injury interrupts that process.

It also means Bosa will not face Arizona on the anniversary of the injury that began his previous recovery. Instead, the 49ers will have to manage his absence while trying to keep a defensive line that has already taken repeated hits functional.

ESPN described the calf injury as the latest and potentially biggest blow to a San Francisco defensive line that has lost multiple players in a short period.

The team will now rely more heavily on the remaining healthy defensive linemen while waiting for other players to become available.

The return of Bosa will also be closely monitored. The prevailing belief is that he will not play for a couple of weeks as opposed to sitting out for yet another season, but the time frame could alter as he goes through his rehab process.

It is a further interruption for a player who has just come back from an injury to the ACL ligament.

The Cardinals game was supposed to mark a symbolic point in Bosa's comeback — nearly one year after the injury that kept him out of the previous season.

Instead, the matchup will arrive with Bosa on the sideline and the 49ers facing a much broader defensive-line problem.

San Francisco's immediate challenge is now straightforward but significant: get Bosa healthy, manage its limited IR options and find enough healthy defensive linemen to cover the workload while its injured players work their way back.

For Bosa, the focus shifts once again from playing on Sunday to getting back on the field.

And for the 49ers, a comeback story that had been gathering momentum has suddenly become another entry on an already crowded injury report.