The winless Redskins didn't think this season of horrors could get much worse. Yesterday it did.

Although playing one of the league's supposedly weaker teams, the Redskins fell behind by 17 points before the game was 18 minutes old and never came close to breaking a losing streak that has grown to five.

By the time San Francisco (3-2) had finished its 30-17 victory at RFK Stadium, quarterback Joe Theismann had been benched for rookie Tom Flick, and most of the 51,843 fans had left after witnessing another afternoon of erratic, mistake-prone play by the Redskins.

Coach Joe Gibbs said afterward that Theismann would continue to start, despite his departure with 5:41 left in the third quarter after his second interception. Flick also had two passes intercepted.

"It was my feeling at the time that Tom should go in," said Gibbs. Asked who his starting quarterback would be, Gibbs first said he would have to think about it. Later he said: "Theismann is still our starter."

Theismann declined to comment on his benching. But he said at times it felt as though only two people were cheering for him: "my wife and my son."

Gibbs admitted this loss was the toughest yet, in part because the Redskins took a step backward after making at least some progress every week. The last time the team was 0-5 was 1965.

Only their special teams, thanks to the return work of a healthy Mike Nelms, were effective. That was hardly enough to offset the club's other problems.

Besides the four interceptions, Washington lost two fumbles, committed seven penalties, dropped at least a half-dozen passes and missed numerous tackles. San Francisco safety Dwight Hicks turned two of those blunders into touchdowns on a 80-yard fumble return and a 32-yard interception return.

Although Gibbs praised his players' second-half effort after they fell behind, 30-3, General Manager Bobby Beathard said he didn't think that "from the very beginning that there was a hell of a lot of intensity. We've had injuries, but you have to compensate for that by playing like hell.

"It seemed like they (San Francisco) ran at will or passed at will. Some teams make timely big plays; we make timely mistakes."

Beathard, like the rest of the Redskins, also is aware that Washington has lost to three teams (New York Giants, St. Louis, San Francisco) that appeared to have comparable personnel. "The schedule certainly doesn't get any easier from now on," he said.

Beathard said he remains confident in Gibbs. "It's never entered my mind to question the coach or the staff. He'll go down eventually as a great coach. And I don't think anyone in the front office feels otherwise."

Owner Jack Kent Cooke, asked about his team's performance, said he had no comment.

The Redskins entered the game feeling they had to get off to a quick start to prevent the home crowd from booing, as it had in their last RFK appearance three weeks ago.

To accomplish that goal, they wanted to eliminate the horrendous mistakes that have occurred in every game this season, especially last week in Philadelphia, when the Eagles turned five fourth-period errors into 22 unanswered points.

The Redskins were unsuccessful at achieving either aim.

San Francisco drove 80 yards in 13 plays on the game's opening series to take a 7-0 lead. Then, after Washington moved on its first possession to the 49er 22, another major mistake all but ended the game before eight minutes had elapsed.

Halfback Terry Metcalf swept right end, made his cut and tried to jump over safety Ron Lott. Instead, Lott knocked the ball out of Metcalf's grasp and into Hicks' hands. Hicks caught the fumble at the 20 and outran Theismann down the left sideline for a touchdown and a 14-0 advantage.

Boos filled the stadium.

"I was in the air and he hit me and the ball was out there, but I couldn't get it because I hadn't come down yet," Metcalf said. "I couldn't believe it when he caught it and scored. A fluke play, unbelievable. It changed the game for us. It gave them momentum."

Said Gibbs, whose team was second in the league in turnovers entering the game: "It's the same story. I thought we were ready to play, but our defense is beat up pretty good and they come out and drive on us and score. Then Terry makes a great run, he makes three lousy yards and they wind up scoring a touchdown.

"We just have to find some consistency. But things can't get much worse than it is."

The Redskins' points came on a 34-yard field goal by Mark Moseley in the first half after Washington couldn't get a touchdown despite four plays inside the 49er 15; a 58-yard punt return by Nelms, playing for the first time this season without a cast on his broken right thumb, and Joe Washington's five-yard run. Washington was playing for the first time since hurting his right ankle against the Giants a month ago.

Otherwise, the offense, which led the National Football Conference entering the game, was ineffective until the outcome had been decided, although the Redskins outgained the 49ers in total yards (304-296). Only Joe Washington, with eight receptions and 30 rushing yards, showed well.

Theismann had been leading the NFC in passing yards, but completed 10 of 24 passes for 123 yards after a miserable first half (five of 17 for 58). Flick, rusty after receiving little practice work with the starting unit since the regular season began, had 12 completions in 24 attempts for 118 yards, relying mostly on short passes to his backs.

"The fans have a right to their opinion," Theismann said about the fans' booing, "and you can't avoid hearing it. You think of the times when they were cheering and screaming for you and you hope you can bring them back.

"This isn't a one-man team, it's a 45-man team. But what's most frustrating is that we were making progress, we were getting consistent. Now it seems the train has been derailed."

Flick, the fourth-round draft choice from the University of Washington, said he was certain Theismann still is the No. 1 quarterback. "I'm not trying to compete with Joe. I think he's a great quarterback and I mean that. I felt sorry to see how things went for him today."

Theismann threw his first interception early in the third quarter with the Redskins on the 49er 28. He tried to find receiver Art Monk down the middle in the end zone, but Hicks jumped and caught it at the six.

"Art and I had a mixup," Theismann said. "I thought he was going to stop short and he read the defense differently and went longer. The pass went in between."

Said Monk: "It probably was my fault. The defense they gave us when the play started dictated that I pull up, but it changed and I went long."

Nelms, playing as a nickel back in place of injured Lemar Parrish, who sat out the game, immediately intercepted a pass from Joe Montana.

But on first down, Theismann got a good rush from the 49ers while standing in his end zone and appeared just to toss up a badly overthrown pass. Hicks returned it for a touchdown to give San Francisco a 30-3 lead.

"The pass got away from me," Theismann said. "I thought it had been caught by (tight end) Gregg McCrary. The next thing I knew, it was a touchdown for them."

Gibbs had seen enough. After the ensuing kickoff, he sent in Flick, who had played for one snap in the first half when Theismann was tackled by linebacker Jack Reynolds and slightly reinjured his right thumb.