Quarterback Joe Theismann of the Washington Redskins has been sacked 14 times in the last two games. Dallas got him eight times, St. Louis six.

"It's probably the worst back-to-back beatings I've ever taken; my back hurt more than anything," Theismann said yesterday as the Redskins held their first practice of the postseason while preparing to play the Los Angeles Rams or Chicago Bears in a divisional playoff game Dec. 30 at RFK Stadium.

It is, perhaps, in synch with the rest of his curious 1984 season that Theismann looks back on these same games and says, "Besides the Green Bay game of last year (398 yards passing), I think these games could be among the best of my career."

Theismann, 35, added, "You know, I was just thinking the other day how, when Mark Moseley set all of the (kicking) records in 1982, I told him, 'Mo, your next season will be your toughest.' Turn around and one year later look who winds up in the same boat. Me."

Such is the price of winning the league's most valuable player award. Moseley won it in '82 and Theismann won it last year. The pressures for the MVP are several: the spotlight gets hotter, the expectations go higher.

This season, Theismann's resourcefulness has been greater than his statistics. Sure, he had some precise throws against the Cowboys and Cardinals, but the most crucial play he made in each game required more savvy than spiral.

He made the key block that allowed wide receiver Art Monk to gain 18 yards on an end-around in the game-winning drive in Texas Stadium. And he made the nine-yard scramble for a first down on the game-winning drive against St. Louis.

No, Theismann has not duplicated his exceptional season of 1983, when he threw 29 touchdown passes and only 11 interceptions, and ran the two-minute offense with a conductor's cool.

This season, he had 24 touchdown passes and 13 interceptions. He had high-efficiency games against Indianapolis (85 percent completion rate), Minnesota and Buffalo (79 percent).

He also had a three-interception misadventure in the 16-10 loss at Philadelphia five weeks ago. Before that, he had completed only 21 of 41 passes in a 37-13 loss to the Giants. And too often, it seems, he has thrown into crowds.

As he leaned against his locker at Redskin Park yesterday, he pondered his 11th season with the team and said, "I have nothing to be ashamed of this year. In fact, I think this season has been better for me than last year, when you consider all of the circumstances."

He did not make the Pro Bowl for the first time in three years. The conference quarterbacks selected were San Francisco's Joe Montana and St. Louis' Neil Lomax.

"I think Neil had a great year and Joe Montana had a sensational year," Theismann said. "I feel I deserved it as much as anybody. I also feel that both of them deserved it, as well."

Many potentially distracting things have happened since the Los Angeles Raiders beat the Redskins, 38-9, in the Super Bowl in January.

Asked how he would respond to the question, "Joe, I haven't seen you since the Super Bowl; what's new?" he laughed and said, "I'd probably say, 'Got a week?' "

The answer might take that long, too. Although he was granted a renegotiated two-year extension to his contract (taking him through the 1987 season and his 38th birthday) during the preseason, the deal has not been signed. Neither Theismann nor team owner Jack Kent Cooke will comment.

After the Super Bowl, Theismann stopped speaking with the media, except after games. That changed in the 13th week of the season. He reverted to his old, more talkative ways, he said, "because I think I have some things to say."

Theismann separated from his wife Shari and is courting actress Cathy Lee Crosby. When the Redskins' passing game became inconsistent in the first portion of the season, Coach Joe Gibbs blamed injuries to key receivers. Other observers, however, implied that Theismann's personal life was affecting his play. "That had nothing to do with it," Theismann said yesterday.

"Everything I did this year was done with one goal in mind. It's a personal reason and I don't want to talk about it.

"My life has changed dramatically recently and, I believe, for the better. Every day you learn, but the last couple of years have been an even greater learning experience for me, on the field and off. It's been a growing period. When I am talking about myself as a person, I credit everything to Cathy Lee. She's helped me slow down. She's given me a chance to stop and smell the roses."

At present, he seems most concerned about stopping all of those blitzers. If the Redskins face Chicago, they'll face the league's best pass rush, which had a league-record 72 sacks this season.

"I saw them play the Raiders on television this year," all-pro tackle Joe Jacoby said. "They knocked out two of the Raiders' quarterbacks. Then I turned the channel."

"We've run into a windmill the last two weeks and and we've been cut by the blades," Theismann said. "If we run into another windmill, we'll have to deal with it."

As expected, the Redskins placed rookie tight end Anthony Jones (sprained neck) on injured reserve yesterday and signed running back Rick Kane, who was released from the team three weeks ago.