The conversation that began what is sure to be a week of tumult around the Washington Redskins wasn’t drawn-out, in-depth or even the least bit dramatic. As soon as Rex Grossman threw his fourth interception of the day against the Philadelphia Eagles, offensive coordinator Kyle Shanahan turned to backup John Beck — who hadn’t played a snap in a regular season NFL game since Dec. 30, 2007 — and said: “Let’s go. You’re in.”

On the Redskins’ opening possession of the fourth quarter of Sunday’s 20-13 loss, Beck trotted onto the FedEx Field turf, and cheers — cheers of relief? — filled the stadium. Grossman, the author of 11 turnovers in his five games this season, stood on the sideline and kept his helmet squarely on his head. And both men began a week in which there is only one relevant question to Coach Mike Shanahan: Who’s your quarterback?

“I would never announce that right after a game,” Shanahan said.

Here we go.

“Who knows what’ll happen next?” Beck said.

What happened Sunday: Grossman matched his career high with those four interceptions, and he now has nine on the season, tied with Carolina rookie Cam Newton for most in the NFL. After completing 9 of 22 passes for 143 yards, he has an abysmal passer rating of 66.5. He has re-entered a phase of his career he hoped he abandoned when he left Chicago after six star-crossed seasons: the week-to-week referendum on whether he is fit to run an NFL offense.

“Obviously, I would have liked to have finished what I started,” Grossman said. “They thought that the best answer was to replace me for that specific kind of spark.”

That’s the word Shanahan used — “spark” — when he explained why he removed Grossman for Beck, who completed 8 of his 15 throws for 117 yards. Beck also ran for the Redskins’ only touchdown on a two-yard quarterback draw. And, of paramount importance, he didn’t turn the ball over.

“John has been practicing very well the past couple of weeks,” Shanahan said, “and with four turnovers there, we thought it was time to make a change and give John an opportunity to show us what he can do.”

The rough translation: The quarterback simply can’t give the ball to the other team and expect to keep his job. Grossman, in his ninth season, understands that.

“I didn’t execute,” he said as he opened his postgame news conference. “I mean, I’m sure most of the questions are going to be about the interceptions, so I might as well just go through them with you.”

So he did, in gruesome detail — and he didn’t even have to recount the two balls he threw that the Eagles flat-out dropped. The first interception came on the Redskins’ opening possession, on third and 16 from the Philadelphia 38. Grossman thought tight end Fred Davis could beat his man on a route down the seam near the goal line. He threw the ball up, and Eagles safety Kurt Coleman beat Davis for the ball. Pick No. 1.

The second came from the Redskins 15, when he looked for wide receiver Jabar Gaffney and instead found Eagles safety Nate Allen. The third was egregious, and came at a time when Grossman had already been booed by the home crowd. From the Philadelphia 20 — when a touchdown would have pulled the Redskins within seven — Grossman tried to loft a pass to Davis near the goal line.

“I trusted that he was going to be able to cross the safety’s face on his route,” Grossman said. But Davis didn’t. Coleman, his vision unobstructed, had his second pick.

The fourth was Grossman’s final throw of the day, a third-down pass from the Redskins 39 on which he scrambled left. He thought Gaffney would come back for the ball along the sideline. Instead, Coleman did. Grossman was done, and Beck — who hadn’t taken a practice snap with the first team since training camp — was in.

“There were some things that showed a little bit of rust,” Beck said. Shanahan, though, said, “I thought he did well today.”

Shanahan said he will likely make an announcement Wednesday on a starter for next Sunday’s game at Carolina. That is when the week’s practice begins in earnest. Now, the question becomes how each man handles the situation, whatever presents itself.

“You’ve just got to flush it,” Grossman said. “You’ve got to go back to your core beliefs. I believe in myself no matter if the whole stadium doesn’t or the coaching staff doesn’t. Whatever the situation is, I believe in myself that every single play I’m going to get it done.”

Sunday, that belief led to four interceptions, and his first benching with the Redskins. On Wednesday, Grossman — and all of Washington — will find out whether Grossman’s belief in himself is shared by his coaches.