There seems little doubt that over the last 12 days the Redskins have added quickness, striking power and line strength to their offense.

Unlike last season, they should be able to score more consistently and pose more problems for opponents, although Washington still will not match such teams as Dallas or Oakland, either in personnel or versatility.

But while the draft, trades and free agent signings have bolstered the offense considerably, Richie Petitbon, the defensive coordinator, is being asked to succeed with a defense that has lost more members through retirement than it has gained since last season ended.

Petitbon is highly capable, and he is surrounded by a solid staff. But Redskin followers should not get overly giddy about this team's potential, despite the presence of running backs Joe Washington and Terry Metcalf. For example, what would happen to the defense if a first-string linebacker were seriously hurt in training camp and lost for an extended time?

"We'll mix and match," said Petitbon, the man who made the tough decision last year to bench Ken Houston. "We weren't that bad last season and we'll be okay this year, as long as we don't get injuries. We'll mix up defenses and use a lot of people. It'll work."

But Petitbon is enough of a realist to acknowledge it would take a miracle that even owner Jack Kent Cooke can't produce for the Redskins to avoid injuries this season, either at linebacker or along the defensive line, the other troublesome area. No pro team should be foolish enough to begin a season without at least trying to provide as much depth as possible at every position. In the Redskins' case, to go into September without some defensive roster additions would be risking football suicide.

Certainly it would be foolish to count on the quick return of Brad Dusek, who is now starting to recover from back surgery. Petitbon hopes Dusek might be able to play before the end of the season, which seems more realistic.

And for the defense to improve -- this is the same group that gave up 35 points to Chicago last season -- the Redskins have to get lucky at a number of positions.

The Redskin master plan has Mat Mendenhall, last year's second round choice, starting ahead of Coy Bacon at one defensive end. First, however, Mendenhall has to show he has advanced enough in a season to move from the injured reserve list to a first string spot.

To make it easier for Mendenhall, the Redskins won't ask to play him full time. If he can handle a starting role, then Bacon can be brought in as a pass rush specilist on second or third downs, along with rookie Dexter Manley, an extremely quick Oklahoma State product. Manley ran a spectacular 4.55 in the 40-yard dash in practice yesterday. Karl Lorch then could move inside to tackle on passing situations -- and the sometimes nonexistent Redskin pass rush of last season could change dramatically.

But if Mendenhall stumbles and if Perry Brooks, who once again has been handed a starting tackle job (he couldn't hold that spot last year), falls short, Petitbon will face some major problems. The same goes for linebacker, where vastly inexperienced Farley Bell and veteran Dallas Hickman, who the Redskins prefer to use as a down lineman, are the only backups to Monte Coleman and Rich Milot. And if middle linebacker Neal Olkewicz is hurt, there is no one around to replace him unless Milot is moved inside, where he isn't comfortable.

Maybe that is why Coach Joe Gibbs spent the last practice of his second minicamp watching the defense instead of working, as usual, with the offensive unit.

"We'll sit down Monday and start evaluating every position," Gibbs said. "Then we'll see what we think we need. But I don't think there is any panic right now about any position."

Of course, talk about the offensive changes dominated the camp. Just the addition of Washington, a breakaway threat everytime he touches the ball, and Metcalf has added a dimension to the club that it has lacked for years. Now maybe the Redskins have at least one runner who can get outside and cut around end or catch a pass in the flat and turn it into a long gainer.

But for the unit to be truly effective, the line first must show the improvement Gibbs expects. His quick-release passing philosophy will help pass protection, but he also needs his young prospects to win starting positions -- or have his veterans get better through competition.

Mark May, the No. 1 choice in last week's draft, was overshadowed at offensive tackle during the minicamp by second-year man Jerry Scanlan, who could become tackle Terry Hermeling's major challenger. Rookie Russ Grimm will push for a starting center position and huge Gary Sayre (6 feet 5, 265 pounds) from Cameron State could prove a pleasant surprise at guard, where Fred Dean will challenge starter Ron Saul.

Besides Manley, Grimm and Sayre, other rookies who had a good camp were receiver Charlie Brown and quarterback Tom Flick. Tight end Clint Didier and receiver Jerry Hill also have ability, but they could get caught up in numbers games at both positions. And don't count on Wilbur Jackson as starting fullback quite yet, not after the way Clarence Harmon ran the last three days.

And one final note about Metcalf. He was so determined to return to the NFL after three years in Canada that he accepted a large pay cut, from $250,000 last season to no more than $115,000 this year. But he can make a lot more by exceeding incentives in his contract. So look for him to have a much better season than some Redskins expect. He has always responded well to challenges, especially when they affected his bank account.