Shanahan 'can't believe it's legal' to motion Trent Williams

A motioning Trent Williams is too good to be true for Kyle Shanahan.

The San Francisco 49ers head coach debuted the wrinkle in the divisional round against the Green Bay Packers, adding another new look to his vaunted rush attack. Williams lined up as a fullback before motioning across the line of scrimmage and running into the Packers' defense at full speed. The 320-pound left tackle cleared room for Elijah Mitchell to convert a third-and-1 run with ease.

"Trent mentioned it to me a long time ago, kind of halfway joking. ... He's probably the best guy you could imagine ever doing it," Shanahan told reporters Thursday. "I can't believe it's legal. It's scary for me to even watch."

Williams had a prolific 2021 campaign as a run-blocker and was rewarded with an All-Pro selection. Shanahan said the 49ers practiced the play just once before implementing it against the Packers.

"It's not something that Trent had to practice too much," he said. "He had to just time out the motion with the snap count and run full speed through the D-gap and clean up whoever shows."

The 49ers could break out the play in the NFC Championship Game versus the Los Angeles Rams, though Williams will have to get over an ankle injury first. He missed practice Wednesday and Thursday but has said he expects to suit up.