Fullback John Riggins, breaking an 18-month press blackout, said yesterday that he has never run better or felt better in his 11-year career. But he refused to say whether he would return to the Redskins next season.

Riggins, who will be a free agent at the end of the playoffs, also said he bowed to the fans in RFK Stadium after his 185-yard, 37-carry performance against Minnesota Saturday "because I didn't know what else to do. I could have high-fived them, I guess, but it was spontaneous. How many games do you play when you carry the ball 37 times for 185 yards?"

During the far-ranging press conference that Riggins requested "to let you guys ask all the questions you've been storing up" since he stopped talking to the media, he declined repeatedly to talk about his future plans. This is the final year of his original Redskin contract, which covered six seasons, including an option year.

He said he hasn't thought much about his future beyond Saturday's game against Dallas for the NFC championship. He refused to say that if he played football next year, it would be for Washington and not, for example, a United States Football League team.

"My career is going to last at least another game on Saturday," he said at one point. "I'm really not concerned at this time about next year." Asked later if he still was concerned, as he had been in the past, about leaving football with serious injuries, he replied: "That's something I'll think about after the season."

Riggins last talked at length to the media in June 1981, after he ended a one-year, self-imposed retirement by attending a minicamp at Redskin Park. He since has refused all interview requests and yesterday declined to explain why he won't talk to the press as a matter of course. He indicated he probably will reinstate the blackout today.

"I feel I am running as fluid as I ever had," said Riggins, who has gained 304 yards in two playoff games this season. "It's the same feeling I had the second year I was in the league, with the Jets . . . People seem to make a big deal out of the fact that I'm 33 years old. I was old about five years ago around here, according to some people. If you start believing that you are old, it affects you. I don't think about it and that helps. I don't feel much different from day to day and year to year."

In the press conference, Riggins, who is the highest-paid Redskin at $330,000 a year, also said:

He has gradually lost weight since the end of the players strike and now feels lighter and quicker. "I won't say I've been taking more chances running the last two weeks, but you can do some things a little more freely the way I feel now."

Washington fans are "the best I've ever played for. The people here are tremendous and I really appreciate it." He said he wasn't surprised how kindly the fans have treated him since he returned from his one-year retirement "because the people understand me. If you give 100 percent, that's all they can ask of you."

One of the reasons he retired in 1980 was the last-minute, 35-34 loss to Dallas that ended the 1979 season. "That game had a lot to do with my decision (to retire)," he said. "It took a lot out of me, because I felt that at the time we had things lined up (for the Super Bowl) like we have them now. It looked to me like it was as close as I thought I'd get to the Super Bowl . . . It's really ironic that things have worked out this year the way they have."

The current Redskins team is the best he's played on, and the offensive line is the best he's run behind. "They are great now and in a couple of years, they will be something to behold."

He wasn't sure how much his first serious effort at weight lifting has helped his play this year "but it hasn't hurt it . . . I decided to lift because it was going to be asked of all the players. And the way (weight coach) Dan Riley emphasized it to me, I knew it couldn't hurt me and maybe it could even help me. It was just a matter of missing out on a couple of frosties (beers) after practice."

He doesn't like the Riggo Drill, the end-of-the-practice routine in which he carries the ball repeatedly. But he said he'd rather carry the ball 40 times a game than run 20 and block 20. "Blocking takes a lot out of you," he said. "You may not notice it, but I very rarely absorb a full blow when I run."

Riggins, saying he has waited 12 years "for a shot like this," left no doubt throughout the press conference that he is being motivated by a chance to play in the Super Bowl. He made sure Coach Joe Gibbs knew of his desires by meeting with Gibbs before the playoff opener against Detroit. In that meeting, he told Gibbs he wanted to carry the ball frequently.

"They were afraid they were using me too much and they wanted to spell me a bit," Riggins said. "But I figured we only had two or three games left. You need to carry the ball 20 times a game before you get the feel of what the defense is doing. If you only get it a couple or three times and then they put you back in 10 minutes later, you've got to start all over again . . .

"I told Joe not to worry about me getting tired. If I feel all right, I'd appreciate not coming out of the game.

"The better running backs have the ability to adjust on the run. I am notorious about not paying attention when they draw up blocking diagrams (during the week) because it just doesn't seem it works out that way Sunday afternoon. You get a different picture every time they snap the ball.

"It becomes a rhythm. It's not unlike a baseball player getting into a groove and expecting to get a base hit. I approach the line of scrimmage and feel like I'm going to get four or five yards or more than that. And I think the offensive line gets the same feeling I sense."

Riggins, who gained only 26 yards in the first game against Dallas this season, said one of the keys for the Redskins on Saturday is not falling behind early. "You don't want to be forced to throw the ball," he said. "You want to stay close and run the ball. And I'd like to think that's the way it will go on Saturday."