The joy Joe Gibbs has gotten from winning his first two preseason games as Redskin coach is being tempered by offensive line injuries reaching near-crisis proportions.

One starter, guard Fred Dean, already had been lost until October because of an arm operation. Now, Jerry Scanlan, who replaced Dean, will be out possibly two weeks with bone chips in his knee. Melvin Jones, the other starting guard, has a stretched Achilles' tendon and may not be able to practice this week. And swing tackle Joe Jacoby has been sidelined until a series of tests determines why there was blood in his urine Friday.

With slight injuries also nagging veterans Ron Saul and Bob Kuziel, the offensive line, the team's major rebuilding problem at the start of training camp, again will have to be regrouped.

"Getting guys hurt like this sets us back," Gibbs said. "You hate to see multiple injuries in one area. It's hard to absorb them. In this case, these young guys especially need the practice time. It hurts their development. It does take some luster off what we've accomplished. Coming off the field Friday night, that's what I was thinking about more than anything else."

Gibbs also admitted he is trying to keep his players and assistants from "getting too excited" about the Redskins' back-to-back impressive victories. The team's flashy play has cheered the fans in RFK Stadium, too, especially the flair shown during Friday night's 27-13 triumph over Minnesota.

"We're probably doing a little more in games than I would normally do," Gibbs said, acknowledging he wants the Redskins to make a good impression early. "But because we have a new staff and so many new players, we've got to be able to try a lot of things and see how well we can do them.

"Something we've always got to bear in mind is that this is just the preseason. You can't get too excited. We'll just have to wait until the regular season to see if we are playing harder in the preseason because of the new staff. That's always a danger in our situation. There is a little more effort put into the preseason than you might find on another more established team."

Not that Gibbs is sorry to have won either game. He says the triumphs "are setting a level of performance that I think is good. We are establishing a trend that will help us. I think the fans have had a part in it, too. The players have really responded to their excitement, they've got us going.

"It's up to the coaches now to keep things on an even keel. We've got to make sure we point out all the things they are doing wrong just as much as what they are doing good.

"Would I be this wide open (offensively) next preseason? Well, that's something that I'd have to evaulate at the time."

Gibbs is well aware that while he has called for halfback option passes and unleashed his offense, most coaches tend to be less daring in the preseason. Friday night's victory, for example, meant more to Washington than it would have to Minnesota and long-time Coach Bud Grant.

Still, those injuries to the offensive linemen could have a more long-reaching effect on the Redskins than winning two games. With Gibbs having to make his first major squad cut Tuesday, from 83 players to 60, his decisions have become more complicated, as well as the development of the offense slowed.

The Redskins now have seven healthy linemen: centers Jeff Bostic and Dan Peiffer, rookie guards Russ Grimm and Darryl Grant and tackles George Starke, rookie Mark May and rookie Allan Kennedy. Grimm and Peiffer have just recovered from earlier ailments. Saul, who hurt his knee last week against Kansas City, probably can resume practicing this week. Jones, according to Gibbs, might be able to play in Saturday's contest in Baltimore.

"We might keep some more offensive linemen than we normally would (after the cutdown) because of the injuries," Gibbs said. Thus, both Saul and Kuziel, who was getting little work in practice before developing back spasms, may survive past Tuesday, although it's apparent neither figures in the club's plans this season.

If Jacoby cannot play for any length of time, the team also could begin scaning the waiver lists for backup tackles.

Gibbs, who will spend much of the next two days reviewing his personnel, may begin cutting players earlier than Tuesday, although he has cautiously waited through three minicamps and five weeks of training camp before making any decisions.

It seems certain there will be cuts at running back, where free agent Otis Wonsley's play has created problems for such veterans as Bobby Hammond, George Ragsdale and Rickey Claitt; at linebacker, where veteran backup Dallas Hickman is being pushed by Mel Kauffman, Herb Spencer and Farley Bell, and at wide receiver, where veterans John McDaniel and Ken Harrison are trailing a group of youngsters.

"I don't enjoy this part of it," Gibbs said. "You try to get to know each player personally and it's hard to tell them that even though you like them, you don't think they are good enough to make your football team."

The Redskins will resume practice this afternoon in Carlisle, Pa., before breaking camp Friday . . . Gibbs again praised quarterbacks Joe Theismann (11 completions in 15 passess for 143 yards Friday night) and Tom Flick (five for 10, 61 yards) while also singling out Wonsley (seven carries for 33 yards and two catches for 19) . . . Clarence Harmon has become lost in the shuffle of running backs. He has carried only four times and caught one pass in two games while Wilbur Jackson has received extra work.

Gibbs said he guessed he should be concerned about trying two halfback option passes so early (Joe Washington's 29-yarder to Zion McKinney was good for a touchdown Friday night) "but the cornerbacks will have to respect it and it will help our running game" . . . Worry about the reserve tight ends, who had not been playing well, was eased by Rick Walker's game Friday. "He just needs to relax more," Gibbs said.