If former St. Louis star Terry Metcalf can run a 40-yard dash in 4.7 seconds and meet other test standards, then he could be signed by the Redskins before the middle of May, team sources said yesterday.

Even with the acquisition of Joe Washington just before yesterday's NFL draft, the Redskins still want Metcalf, since they feel having two scatbacks would give their offense quickness it lack last year.

However, before the club will surrender a 1982 midround draft choice, probably a fifth or sixth, to St. Louis as compensation for Metcalf, he first must show General Manager Bobby Beathard and Coach Joe Gibbs he has retained his quickness and agility after three years in Canada. The Cardinals and Washington agreed yesterday on compensation during the draft.

Metcalf is scheduled to work out for the Redskins during next week's three-day minicamp at Redskin Park. Final attempts to sign him could follow the conclusion of that camp.

"If we wind up with Terry, too, look at the changes we have made in our backfield," said one source. "We've gone from having a lot of medium-speed guys to have some real quickness."

Last season, the Redskins started Clarence Harmon at halfback, with Buddy Hardeman, Ike Forte and Bobby Hammond in reserve.

Metcalf, 29, was a standout with the Cardinals both as a runner and receiver before signing with the Canadian Football League. He was released by Toronto this month, making him a free agent.