It has reached this point with the Washington Redskins and their quarterback situation: No one knows who will start one week to the next. Coach Mike Shanahan may or may not be forthcoming with such a decision as he prepares his team for an opponent. And the reasoning behind making a choice might seem convoluted.

What is certain, at this point, is it hasn’t made any difference, because neither John Beck nor Rex Grossman has won a game in a month-and-a-half, and a once-promising season now appears beyond repair.

So it was Sunday at Sun Life Stadium, where Grossman made his first start in four games, Beck looked on wearing a baseball cap, the Redskins endured a nearly unwatchable 20-9 loss to the Miami Dolphins, and a new week with the same stale questions about quarterback play began.

“Well, we’re still going to do the same thing,” Shanahan said when asked how he would approach the situation going forward. “We’re going to look at the scenario, what gives us the best chance to win, and make the decision based on that.”

Last week unfolded this way: Beck managed to produce only two touchdowns over the previous two weeks. Though Shanahan said following a Nov. 6 loss to San Francisco that he would stick with Beck for a fourth straight game — “That was my intention,” he said Sunday — he rethought the situation over the course of the week.

Right tackle Jammal Brown suffered a groin injury against the 49ers that kept him out Sunday. That provided further instability to an offensive line that already featured rookie seventh-round pick Maurice Hurt, who would play his second NFL game at left guard. Beck, 30, is in his fifth NFL season, but he has appeared in only nine games, all losses.

Shanahan seemed to imply that the fact that Beck took 10 sacks Oct. 30 against Buffalo but then dumped the ball off too quickly to avoid pressure last week against San Francisco both factored into his decision to go with Grossman. Grossman’s last appearance? A four-interception day Oct. 16 against Philadelphia.

“You’re playing with an inexperienced quarterback and you just don’t want to throw him to the wolves,” Shanahan said. “You go with more of an experienced guy that has dealt with these situations. I didn’t want to put John in a situation where we had a number of guys down, and with his experience, especially over the last two weeks, I didn’t think that was the right thing to do.”

So during the week, Shanahan began splitting snaps between Beck and Grossman. On Saturday morning, he told Grossman he would start for the sixth time this season. Grossman was asked whether he was surprised. His response spoke to how unstable the position is.

“Yes and no,” Grossman said, pausing and sighing, with no explanation.

Against Miami, Grossman completed 21 of 32 passes for 215 yards with two interceptions and no touchdowns for a passer rating of 58.7. The first pick came when wide receiver Leonard Hankerson slipped and fell. The second came in the fourth quarter on first and goal from the Dolphins 10, and it took away any chance the Redskins had of winning. The Redskins trailed 13-9, and Grossman looked for Hankerson toward the back of the end zone. Miami linebacker Karlos Dansby read the play perfectly, and picked it off.

“I’ve got to be more careful with the ball, especially first down in the red zone, a crucial point in the game,” Grossman said, “but at the same time, we hadn’t scored, and I was trying to put one in there, and that was a critical point in the game.”

Beck departed the locker room without speaking to reporters. Players, though, seemed upbeat about the change, if only because Grossman more frequently looked downfield. Against San Francisco, Beck failed to complete a single pass longer than 17 yards. Grossman had five completions that long or longer Sunday.

“It gave us a spark,” left tackle Trent Williams said. Grossman “got the ball downfield. He came in, did everything we asked. Rex played his butt off. He threw the deep ball.”

Whether or not he has that opportunity next week against Dallas is uncertain.

“I don’t know,” Grossman said. “. . . I’m just here to play.”

Grossman has completed 113 of 197 passes (57.4 percent) for 1,347 yards with six touchdowns and 11 interceptions and a rating of 65.3. Beck is 80 of 132 for 858 yards with two touchdowns and four picks for a rating of 72.1. In a season gone bad, they are Shanahan’s choices, and no one knows how they’ll be handled.

“Change week by week, like I told you,” Shanahan said. “We just got to keep on fighting and do what we think gives us the best chance to win based on the number of situations — could be the defense, could be personnel. But we’re going to do what gives us the best chance to win, and that’s the bottom line.”