Maryland will get an early jump on the 1981 basketball recruiting season today when Jeff Adkins, a 6-foot-4 guard from Martinsville, Va., announces he will become a Terp next season.

Meanwhile, American University Coach Gary Williams has suffered a loss, even before the Eagles open their season tonight at Rutgers.

Ray McCarthy, a 6-8 sophomore, who would have started or been the first front-line substitute for AU this season, has decided to transfer to St. Joseph's, where he will be coached by former American Coach Jim Lynam.

"He just walked into my office and said he was going to transfer to St. Joe's," Williams said of McCarthy, who is from Philadelphia. "I really think it's a shame because he would have played a lot and, I think, helped us a lot, this season."

McCarthy will be eligible to play for St. Joe's beginning in January 1982.

Adkins, who can play point or wing guard, was recruited by Maryland, Notre Dame, North Carolina and Virginia.

He is considered good enough by some observers to step into the spot that will be vacated when Greg Manning graduates at the end of this season.

One other recruiting note: Pat Ewing, the 6-11 center from Cambridge, Mass., generally considered the best high school player in the country, reportedly has narrowed his choices to Georgetown and Boston College. Ewing also is expected to announce his decision early, perhaps by Christmas.