Just one day after returning to practice from a two-month absence because of a sprained left arch, Washington Redskins running back Gerald Riggs received considerable work with the first unit in workouts yesterday at Redskin Park. The Redskins, however, were not particularly enthused by the reason Riggs received the extra work.

Rookie Brian Mitchell, who missed practice the previous two days because he was in Louisiana with his father -- who suffered a serious heart attack -- was on the artificial practice surface only a few minutes when he re-injured an ankle he slightly sprained in Saturday's 25-10 win at New England.

After examining Mitchell, trainer Bubba Tyer said he believes Mitchell will be able to play against the Colts Saturday in Indianapolis.

Coach Joe Gibbs has said all week he is reluctant to use one of the Redskins' two remaining free moves this week, but he said late yesterday he would consider activating Riggs if Mitchell were declared unable to play.

"Gerald looked very good out there, and I haven't talked to him yet about how he felt," said Gibbs. "We would prefer not to make a move, but if Brian was definitely out, we would have to consider activating Gerald."

Gibbs said even if Riggs were activated, he likely would not be used. Earnest Byner has been getting virtually all of the carries in Washington's one-back offense as the Redskins (9-5) have won four of their last five games.

"We would {activate Riggs} only to have him available in case of an emergency. That's all," said Gibbs.

Mitchell could be one of the two inactive players against the Colts. Defensive end Markus Koch (sprained left knee) did not practice again yesterday and likely will be on the inactive list.

"We might just play one {running back} short and put {Mitchell} on inactive if he can't play," said Gibbs. "That just means we would suit up {quarterback Gary} Hogeboom."

Hogeboom has been inactive for nine of 11 games since being signed as a free agent.

While their own running back situation was a cause of concern, a Colts running back was prevalent in Washington's thoughts too.

However, the Colts' Eric Dickerson has not been the center of attention that he had been throughout his eight-year career. After returning from a six-game suspension to begin the season, Dickerson started slowly and the Colts were losing. The team's focus gradually shifted to the passing game and rookie quarterback Jeff George.

Dickerson, in an uncharacteristic way -- quietly -- is beginning to regain his form as the Colts (6-8) cling to slim hopes of gaining an AFC playoff berth.

What the Redskins would like to do is slow down Dickerson and force George into long passing situations.

In Sunday's 29-21 victory over the Jets, Dickerson rushed for 117 yards and two touchdowns and caught five passes for 45 yards. Eleven of his 28 carries produced first downs.

On Nov. 25, Dickerson had a season-high 143 yards rushing in a 34-20 upset of the Bengals.

"He is at the top of his game right now," said Washington's right defensive tackle, Darryl Grant.

But between those two games, Dickerson was held to 60 yards on 17 carries by Phoenix and to 33 yards on 12 rushes by Buffalo. The Colts lost both games.

"Dickerson is still the focal point of that team as far as we are concerned," said Redskins linebackers coach Larry Peccatiello. "Dickerson is the guy who always commands respect."

Gibbs said Dickerson still can be as productive as he was with the Rams and in his early days with the Colts.

"I think he is starting to get back to where he was," said Gibbs. "But it is not just Dickerson. It is both their backs with {Albert} Bentley too. They split you out by using both of them, and if they can get either one of them outside, they will hurt you."

Peccatiello said the Redskins will try to force the Colts inside toward tackles Grant and Eric Williams.

"The problem Dickerson possesses is that he has the great speed to bounce things outside when you have taken away the middle," said Peccatiello. "All you can do is try to emphasize good force principles from the outside."

The defensive line, which did not play the run particularly well in a five-game stretch in which the Redskins allowed 140.4 rushing yards per game, has been outstanding since. In the past three games, all victories, Washington has allowed an average of 68 yards rushing.

With George's improved play, the Colts somewhat neglected the running game they had built around Dickerson. But over the past four games, Dickerson has averaged 20 carries, and after the win over the Jets, Coach Ron Meyer said he was intent on re-emphasizing the running game with Dickerson.

The Redskins prepared this week taking Meyer very seriously.

"We expect to see Dickerson a lot," said Peccatiello.

Redskins Notes: No month has been as good to Washington in the past 10 years as December, and this season has been no exception.

The Redskins have the NFL's best December record of 27-8 (.771) since Joe Gibbs became coach in 1981. They have won their last seven December games, including three this season. In all other games under Gibbs, Washington is 84-45 (.651). . . .

Indianapolis has been a much better team away from home this year, going 4-3 on the road, 2-5 at the Hoosier Dome. . . . The Colts have not allowed a 100-yard rusher in 17 straight games. Byner has rushed for at least 100 yards in the Redskins' last four victories.