The Baltimore Colts defeated the Washington Redskins, 21-10, today at Carlisle High School in a scrimmage that, all at once, revealed the strengths and frailties of the Redskins' offensive line.

It also revealed a human frailty in Frank Kush, the Colts' strong man head coach. Today, his players worked hard for him. Nobody poured root beer over his head.

Consequently, Kush revealed a teeny postgame smile.

"I could almost see our players say, 'Hey, were not so bad after all,' " said Kush, whose team washed up in an 0-8-1 tidal wave last season. "When you have had as hard a time of it as we have, any win is beneficial."

Certainly, the Colts' defense didn't seem so bad in a scrimmage that began with one-on-one pass blocking drills and moved to seven-on-seven passing drills. Scoring was kept only in the 11-on-11 scrimmage, in which teams alternated 10-play possessions, beginning from midfield or either 40-yard line. There were no punts or kickoffs.

The Colts' defense recorded four sacks, making life miserable for reserve quarterbacks Bob Holly and Babe Laufenberg, each of whom was sacked twice. All the sacks came after the starting offensive line--the Hogs--had left following Washington's first and most impressive possession.

"I think, very obviously, we had some problems with our offensive line today and it affected our quarterbacks," said Washington Coach Joe Gibbs.

"This was probably a bad day for our reserves (on the offensive line)," said Joe Bugel, the offensive coordinator. "Yes, I'm concerned."

With an overflow crowd of 9,000 sitting in grandstands that heat and high humidity made seem more like a frying pan, quarterback Joe Theismann led the Redskins on a powerful first-possession drive behind the Hogs that ended with Mark Moseley's 22-yard field goal.

"It was fun," said offensive tackle Joe Jacoby.

"We're to the point where we have enough confidence and experience to know what we are doing," theorized center Jeff Bostic.

The first drive could have produced a touchdown, but Theismann's quick third-down, slant-in pass from the Baltimore five-yard line, to wide-open tight end Don Warren, was incomplete in the end zone.

"A little too hard, a little behind him," said Theismann, who completed four of five passes for 33 yards in the scrimmage and looked stiletto-sharp.

However, the Redskins did not score again until nearly 1 1/2 hours (or four possessions) later, when rookie running back Marcus Gilbert ran two yards for his third tough-it-out touchdown in two scrimmages against the Colts.

In between Redskins' scores, Colts' quarterbacks Mike Pagel (seven-yard touchdown run) and Mark Herrmann (one-yard touchdown run) produced scoring drives. Running back Randy McMillan ran one yard for the touchdown that gave the Colts a 21-3 lead, an advantage as large as it is rare for Baltimore.

A scoring opportunity for the Redskins evaporated in the heat when quarterback Tom Owen passed into the end zone for wide-open Van Heflin, a first-year tight end. But the ball bounced off Heflin's chest and into the arms of defensive back Nesby Glasgow.

Fullback John Riggins sat out the 11-on-11 scrimmage. Running back Joe Washington, who played sparingly in the scrimmage, stood near Riggins on the sideline, wearing a towel over his head. Theismann sat on his helmet after he left the field following the first possession.

But the offensive line was a bit troublesome.

With starting guard Mark May out for several weeks with a partial tear of his right triceps muscle, Don Laster started.

Laster is the 6-foot-5, second-year player who weighs 300 pounds and has been instructed to drink eight quarts of water a day to avoid dehydration. Laster said he feels strong enough, with breaks, to play more than half a game.

Darryl Grant played at right guard, too. Grant is the starting defensive right tackle who was moved to May's spot Thursday because the Redskins do not have much depth on the offensive line.

"Laster started (over Grant) because he's been there for a year and Grant has been on offense for two days. I just wanted to see what Donnie could do," said Bugel.

"Just getting through the preseason will be tough. I don't want to use Jacoby and Russ Grimm (starting left guard) for every minute of every exhibition game," said Bugel. "That would be ludicrous, to drive them into the ground. At times, you may look bad, you may stink up the joint, but you have got to look at some of the young guys . . . I'm concerned because we don't have any depth at tackle. We've got Jacoby and George Starke and Donnie, who it's tough on now, having to play guard.

"Now, we lose Mark May for a while. He's been a stalwart and losing him, without a doubt, is devastating to our line."

The Redskins scrutinized rookie offensive linemen Bob Winckler, Todd Hallstrom, Nathan Newton and Jay Bequette today. After four sacks worth of doubts, Redskins officials might start looking around the league for other competent linemen. They aren't easy to find.

"It's tough when you start out as a rookie on the offensive line," said Jacoby, in his third year. "I remember giving up sacks then, too."

Providing the standard postscript to another scrimmage, Gibbs said, "I'm sure we'll have a lot more to say after we look at the films tomorrow."

Defensive end Dexter Manley suffered a sprained right thumb in the one-on-one passing drills and did not play in the scrimmage. Wide receiver Rodney Goosby suffered a bruised elbow in the 11-on-11 scrimmage. . . Owen completed two of six for 25 yards, Holly three of six for 34 yards; Laufenberg three of six for 22 yards . . . Gilbert (six carries) and Clarence Harmon (three carries) led Redskins' rushers, each gaining 16 yards . . . Theismann completed two passes to Charlie Brown, for 16 and seven yards.