Redskins fans got only a short glimpse of rookie safety Phillip Thomas, right, closing on on Shonn Greene, center, with London Fletcher in the preseason opener, in action. (John McDonnell/The Washington Post)

RICHMOND — Safety Phillip Thomas will miss his entire rookie season with the Washington Redskins because of the injury to his left foot that he suffered during Thursday’s preseason-opening win at Tennessee.

Coach Mike Shanahan said Tuesday at the team’s training camp that Thomas will undergo surgery and will be sidelined for four to five months after he was diagnosed as having a Lisfranc injury, a serious mid-foot injury. Thomas will be placed on the season-ending injured reserve list, according to Shanahan.

Thomas was hurt during the preseason opener. Shanahan said Saturday that the team did not believe he had suffered any fractures or a Lisfranc injury. But he was sent to be further examined by Charlotte-based foot specialist Robert Anderson, and Shanahan said further tests showed the extent of the injury.

Phillip Thomas Thomas injured his left foot Thursday. (John McDonnell/The Washington Post)

Thomas was a fourth-round draft choice by the Redskins in April out of Fresno State. He fell behind after missing a week of offseason practices due to an NFL rule prohibiting players from attending such activities until their classes graduate at their schools. But he said during training camp that he was catching up and getting positive feedback from the coaching staff. He started the preseason opener alongside fellow rookie Bacarri Rambo at safety, with veteran Brandon Meriweather being withheld from that game as he works his way back from last season’s knee injury.

“You lose a guy [and] competition still goes on,” Shanahan said. “These guys are one play away from being the starter. We’ve got a lot of quality players out there.”

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What’s ahead:

● Chase Minnifield and Aldrick Robinson’s scuffle at practice, and Mike Jones’s observations.

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