Rex Grossman said Mike Shanahan called him into the head coach’s office at Redskins Park Tuesday and told him John Beck would be the Redskins’ new starting quarterback.

“I was frustrated,” Grossman said Wednesday. “Not completely surprised, but disappointed that I wasn’t able to come back off that game.”

Grossman acknowledged his poor play in Sunday’s loss to Philadelphia but said he feels he should remain the team’s starting quarterback because of his performance through its first four games.

Rex Grossman (8) is pursued by Philadelphia Eagles defensive end Darryl Tapp (55) Sunday(Jonathan Newton/The Washington Post)

“I had an opportunity to make it clear as day, and it wasn’t. For the first four games, I played well. I could show you to prove it, but it doesn’t matter. At this point, it is what it is.”

Grossman won the starting job by beating out Beck in a preseason position battle. Though Shanahan said it was a close race and has spoken positively of Beck, Grossman said he never felt he was on a short leash.

“I felt secure in my job,” he said. “So that wasn’t the case at all.”

Grossman wouldn’t reveal exactly what Shanahan told him Tuesday but said turnovers have been a big problem. Grossman was responsible for every Redskins turnover this season: nine interceptions and two lost fumbles.

“Whatever you want to say about turnovers, there’s always a reason,” he said, “but ultimately, I’m responsible for the ball.”

Grossman assumed the backup quarterback duties on Wednesday, meaning he will have very few snaps with the first-team offense. But like Beck through the first six weeks, Grossman knows he’s just a play away from being the team’s top quarterback again.

“I’m a professional. I’m going to go about my business the same way,” Grossman said. “I know this offense. If I do get back in there, I’m gonna feel real good about it. I’m gonna feel real good about where I’m at. Just try to get better and build on the things I did well. Having success and winning games will propel my confidence, if I do get back in there. Obviously, there’s things I need to clean up, but for the most part, I’ll be in a good frame of mind.”