Mike Thomas, who had previously practiced only three days the entire NFL preseason, ran at full speed at Redskin Park yesterday and coach George Allen said his 1,000-yeard rusher will start and play at least a quarter against the New England Patriots in Sunday's fifth exhibition game.

But all the news was not good for the Redskins this hot, muggy day.

Dave Butz, the starting left defensive tackle, watched the drills from the sideline, a result of a stone bruise on his right heel caused by what he said were shoes he wore in the Green Bay game that did not fit properly. He said his status was questionable for Sunday's game at Foxboro, Mass.

And rookie wide receiver Kevin Farrell was overcome by heat and taken by ambulance to nearby Access Emergency Medical Center.A hospital spokesperson said he was suffering from heat exhaustion but was in good condition and would not be kept overnight.

Thomas and wide receiver Frank Grant, whose leg problems had kept the trainers busy in the past two weeks, were a welcome sight for Allen.

"I had to blink my eyes and look twice," the coach said in reference to seeing his first offensive unit intact for the first time this preseason.

Thomas feels he is on schedule for being ready for the regular-season opener Sept. 18 against the New York Giants. Privately, some of his teammates have expressed resentment over the fact that Thomas signed a $110,000 contract and has practiced so little.

"There's an old school and there's a new school," said one Redskin veteran. "The old school said you practiced and played at any cost. The new school is more conservative, especially in the preseason.

"Look at McDole, Hauss and Talbert. There's a reason they've played so long. They work hard. They never miss a practice. They practice hurt. Some guys don't know how hard they can work, and they never push themselves to find out."

What concerns Allen is that unlike Larry Brown and Tommy Mason, who did not play until late in the exhibition season, Thomas has not been able to get the work in practice that those former Redskins did.

"It worried me," Allen said after practice yesterday, "and I talked to Mike. He'll start and he'll have a good game, he knows now is the time."

Thomas said he still has not fully recovered from the leg injuries that hampered him throughout the 1976 season when he gained 1,101 yards. That is the major reason he has not pushed himself thus far.

"I know what's best for me," Thomas said. "It's about the right time now, two weeks before the opener. I'll get my bumps and bruises and maybe get a headache or two. I'll be ready."

Allen has been complaining throughout the preseason about mistakes and lack of concentration, a malady he blames for 408 penalty yards called against his team in four exhibition games.

Now, the offensive line - one of the Redskins' strengths - will have two weeks to readjust to Thomas' style of running as compared with Calvin Hill's.

"I don't think we'd aim to go around the corner as much with Calvin," said left tackle Tim Stokes. "With Calvin you anticipate a cutback. Calvin takes longer strides. So you try to give him more depth so he can anticipate his cuts better.

"The great thing about Mike is that he can find a hole anywhere. He has great peripheral vision. He's so elusive, it's tough to get a good shot at him. Mike is so quick you don't have to hold your block very long. He makes us look a lot better than we are. They are both great backs; they just have different styles."

Meanwhile, the 6-foot-7, 285-pound Butz said he was able to put pressure on his right heel for the first time yesterday since the Green Bay game.

"I've had a problem with my shoes," said Butz, who wears size 12 1/2 EEEEEEE. "I've tried three different pairs of shoes here. The shoe was rubbing and the spikes jumped into my heel and gave me a stone bruise. I was not kicked; it was not sprained or anything else."

With Butz out, Bill Brundige played left tackle and was backed up by Karl Lorch, who was impressive with three sacks as a left defensive end against Green Bay. Kick returner Eddie Brown, who spent three days in Carlisle Hospital last week with an abscess in his throat, was back returning punts yesterday.

Pat Fischer ran early at Redskin Park in his attempt to overcome a pinched back nerve. The left cornerback, a 17-year veteran, did not stay for practice. Fischer has yet to run backwards or cut sharply . . . Bob Brunet's stepsister was killed in an automobile accident in Louisiana Monday and the special-teams standout went home for the funeral and is earliest . . . Allen is working Reggie not expected back until tonight at the Haynes at fullback this week and said the added versatility would give the second draft pick a better shot at making the team. Haynes, who was drafted as a tight end, was an All-America JUCO fullback, Allen said . . . Conditioning coach Jim Curzi helped the trainers in giving the players water yesterday and noted, "That's like watering a herd of elephants." . . . Allen liked the humid weather."Let's hope it's like this tomorrow and the next day," he said. "The veterans haven't had this Death Valley conditioning weather like the rookies had at Carlisle." . . . New wrinkles at Redskin Park this season: a downhill slope for the defensive backs to improve their backpedaling speed and a platform tennis court that is under construction. "It's a good game to relax and keep in shape," Allen said. "They can play it on Mondays and when they have Tuesdays off."