Reports leading up to the game suggested McCaffrey was likely to play as he recovered from a calf injury in early August.

On Monday evening, about 90 minutes before kick-off, it was suddenly reported that McCaffrey would be inactive.

If Mason had actually been told that McCaffrey would not start Friday, the 49ers would face fines and penalties from the league office for hiding an injury.

49ers coach Kyle Shanahan strongly denied Mason’s comments immediately after the game.

“I never told Jordan he was going to start,” Shanahan said after the game. “I told him to be ready, but it could have been Bobby (Turner) or somebody trying to get him fired up. He knew he was going to have to play a lot, it wasn’t going to be like normal.”

Reporters asked Mason during the postgame press conference if McCaffrey would play against the Jets.

“That question is exactly why I’m angry, that’s why I don’t like to talk to the media, because if you say one thing wrong, … and you know … we’ll skip that question,” Mason said.

Mason tore through the Jets’ outmatched defense during the game, carrying the ball 28 times for 147 yards and a touchdown, while also catching his only target for six yards.

ESPN’s Adam Schefter also reported just before Monday’s game that McCaffrey’s calf injury aggravated on Friday and he will not only miss the first week, but will also be benched for the second week against the Vikings.

“On Friday, Christian McCaffrey withdrew from training,” Schefter said“They weren’t too worried, they didn’t think it was a big problem, they thought and expected that he would be able to go tonight.

“The problem was that he came in for treatment today and the calf was still stiff. Let’s keep in mind that he hasn’t actually trained all summer, it wasn’t just a calf, it was also his Achilles tendon, so you have two problems here. They decided, in the interest of a long season, to sideline him tonight.

“Not only is Christian McCaffrey out tonight, but there’s a real chance he won’t play Sunday either. They’re playing on grass in Minnesota on a shortened week… He’s out tonight and it looks like he won’t play Sunday either.

San Francisco did fine without him in Week 1, beating the Jets 32-19. Regardless of who starts at running back, they should be the heavy favorites over the Vikings.