Mullens already had the play call figured out and was trying to relay the information to his teammates in the huddle, but Shanahan was still speaking.
"He was like, 'Can you just shut up?'" George Kittle said of Mullens while describing the situation.
The 49ers tight end found the one-way exchange hilarious.
"Sometimes in the huddle, you know you hear the play call, and you're ready to repeat it," Mullens said via Brad Almquist of KNBR when asked about the story. "So yeah, I was just ready to call the play."
Shanahan joined KNBR on Friday afternoon and shared his side of the story.
"That was [Mullens'] first game with [the radio]," Shanahan explained on the "Tolbert & Lund" show. "I promise you it will happen probably three more times this Monday. When you are yelling in someone's ear and the microphone in their ear — it's in their ear because it's in their helmet, and it's turned pretty loud because it's got to be able to handle all the crowd noise and stuff like that, and I'm pretty intense on game day. I don't whisper it to him. I yell it pretty loud.
"Lots of times, you've got to say it again because you've got some wordy stuff and they want you to repeat it. And sometimes I repeat it when they need it. Sometimes I repeat it when they don't. It's very hard when you're trying to talk to 10 other guys in the huddle, and you've got some annoying coach yelling in your ear, and it's hard to communicate."
Shanahan certainly understands what Mullens was thinking during the situation — even if he could not hear his quarterback. Again, it is a one-way radio. Shanahan has been there before and shared a story from when he was the offensive coordinator under head coach Gary Kubiak while with the Houston Texans.
"One of my first times calling plays in Houston, I'm sitting there, the clocks going, and I'm trying to think about a big third-down call," Shanahan said, "and you've got a thousand things going into your head at once. There were a few people yelling into the headset and one person, in particular, was yelling and I just yelled to shut up out of panic, just like probably Nick did in the huddle, just so I could think so I could spit the play call out.
"Right after the end of the play, I realized it was Gary Kubiak, the head coach.
"I had to talk to him about it after the game. Just like, 'I promise you, I did not mean to do that. It was just impulsive, and I was panicked. I was trying to think.'"
You can listen to the entire conversation with Shanahan below.
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