49ers to be 'very careful' with star player's injury

Many were surprised when 49ers star running back Christian McCaffrey was listed as inactive in Week 1.

However, as more information emerged about why he missed San Francisco's regular-season opener against the New York Jets, it became increasingly understandable.

It was revealed that McCaffrey is dealing with a calf injury and Achilles tendonitis, which is an injury that tends to linger.

Head coach Kyle Shanahan wants to get ahead of the injury early in the season to prevent reaggravating it.

"It's not just the calf, it's the Achilles, and the Achilles is tendonitis, and that stuff comes and goes," Shanahan said via Kevin Patra of NFL.com. "When it is acting up, it's something you've got to be very careful about."

That could mean at least another week on the sideline for McCaffrey. NFL Network insider Ian Rapoport seems to think that will be the case, naming him a " long-shot " for San Francisco's Week 2 matchup against the Minnesota Vikings.

Luckily for the 49ers, they ran the ball exceptionally well in McCaffrey's absence, thanks to third-year running back Jordan Mason.

The 25-year-old had 28 carries for 147 yards (5.3 yards per carry) and one touchdown in San Francisco's 32-19 win on "Monday Night Football." He also registered one catch for five yards.

Mason's impressive play will allow the 49ers to make sure their star player is fully healthy before letting him return to the field, but Shanahan noted that if it were the postseason, McCaffrey would be playing.

"Definitely, I believe if it was a playoff game, he would've played," Shanahan added. "Christian's very diligent about that stuff. And if it was a playoff game, he made it very clear to me he believed he could go. But when you hear that type of stuff, and it's not a playoff game, and it's Week 1, and especially when you're dealing with the lower extremities like that it, it was a tough decision. But hearing all the words and stuff, in the long run, it made it easy."