Washington Redskins quarterback Robert Griffin III has been fined $10,000 by the NFL for an apparel violation, a person familiar with the league’s action said.

The fine was assessed to Griffin for wearing unauthorized apparel during pregame warmups prior to Monday night’s preseason game against the Pittsburgh Steelers at FedEx Field, the person said, speaking on the condition of anonymity because the fine had not been made public. The person did not specify which article of clothing caused the violation.

Players are prohibited from wearing unauthorized apparel during the period on game days when they are visible to the stadium and television audiences, including pregame warmups.

Griffin did not play in the game Monday night. The Redskins plan to withhold him from the entire four-game preseason as he works his way back from knee surgery in January. He did drills on the field before the game Monday night wearing a shirt that said, “Operation Patience,” which he said early in training camp he was calling the team’s plan to ease him back toward full-time duties.

It is at least the second such fine for Griffin, who endorses Adidas. He was fined $10,000 by the league last December for wearing Adidas apparel to a postgame news conference. Nike is the league’s official apparel maker.

Griffin was not available to comment on the fine.

Have a Redskins question? E-mail Mike Jones at mike.jones@washpost.com with the subject line “Mailbag question” for him to answer it in The Mailbag.

What’s ahead:

● On Friday, the team has a walkthrough before Saturday’s 4:30 p.m. game against the Bills.

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