49ers' Christian McCaffrey receivers concerning injury update after Achilles issue

The San Francisco 49ers have officially shelled out the big bucks to keep Brock Purdy as their long-term quarterback.

To help Purdy be his best, the 49ers need Christian McCaffrey healthy and on the field.

SI's Grant Cohn is concerned about McCaffrey's outlook for the season, though.

At different points of last season, CMC dealt with bilateral Achilles tendonitis and then a torn PCL.

Amidst the injuries, McCaffrey averaged an underwhelming 4.0 yards per carry.

"McCaffrey didn't rush back from his Achilles tendonitis last season," Cohn writes. "He was questionable for Week 1 -- the 49ers thought he might be able to play in that game. Instead, he waited until Week 10 to make his debut. And he still averaged just 4.0 yards per carry. And he lasted only four games before he injured something else."

MORE: Shedeur Sanders makes sad (possibly joking) statement on NFL Draft slide

San Francisco traded its top backup RB to Minnesota in the form of Jordan Mason.

The 49ers have second-year back Isaac Guerendo as their best McCaffrey insurance now, and he has promise, but he's not CMC.

Cohn also references McCaffrey's age, now 30 years old, as a reason that the injury recovery might be rough, too.

San Francisco is hoping for the best, but 49ers opponents will hope Cohn's concerns are proved accurate.

MORE NFL NEWS:

• Jets had a savage Aaron Rodgers reason for signing Justin Fields
• Steelers reject $37 million QB decision
• Jamal Adams hints at free agent signing with former team
• Shilo Sanders reveals surprise role with Buccaneers
• Brock Purdy's rise from Mr. Irrelevant is one of coolest stories in NFL history
• Giants wanted division rival's star QB instead of Russell Wilson