MANKATO, Minn. -- In the heat and drudgery of training camp, Minnesota Vikings coach Mike Zimmer has been imploring his players to show more emotion. Zimmer, however, never figured it would put him flat on his back.

Yet that's exactly what happened Wednesday afternoon at the end of a two-minute drill. Quarterback Sam Bradford, one of the most robotic personalities in the NFL, began celebrating after throwing a touchdown pass to receiver Stefon Diggs. In his excitement, Bradford went looking for the first guy he could find. That turned out to be Zimmer, who was standing a few feet away from him in the backfield.

Bradford, his arms flailing, grabbed Zimmer by the shoulders. One thing led to another, and suddenly the 61-year-old coach was on the ground.

Doctors have warned Zimmer about inadvertent sideline contact, which could set back his recovery from a total of eight surgeries to repair a detached retina in his right eye. But he got up laughing and had a few one-liners for Bradford afterwards.

"I didn't see him," Zimmer said, smiling. "It was a blindside shot, but I told him a quarterback can never hurt me."

Bradford was not scheduled to speak Wednesday and was not available to comment after practice.

"They have to show some emotion out there," Zimmer said. "I'm glad he did it. ... I've been on [them] about not showing enough emotion when we make a big play."

Moving forward, a suggestion for Zimmer: Take a few extra steps back when they do.