49ers running back Jordan Mason had an important game on Monday night, filling in for the injured Christian McCaffrey, but when Mason spoke to the media afterward, he was in a bad mood.

Immediately after the game, Mason told ESPN’s Lisa Salters: he found out Friday night that he would start in place of McCaffrey. That would mean the 49ers would have violated the NFL’s injury reporting rules by not announcing that McCaffrey’s injury would keep him out. But between talking to Salters and speaking to reporters at his postgame press conference, someone clearly explained to Mason that his comments could get the 49ers in trouble.

A reporter asked Mason, “When did you find out you were going to be in the starting lineup?” Mason gave a halting answer, seemingly blaming the media for what he had said on national television.

“That’s the question that makes me angry,” Mason replied. “That’s why I don’t like talking to the media, because you say something wrong and then, you know – I don’t know. Just leave that question out of the question.”

But Mason wasn’t wrong to answer Salter’s question honestly. The 49ers were wrong to tell Mason 72 hours before the game that McCaffrey was out, but waited until 90 minutes before kickoff to tell everyone else.