Atlee Hammaker and Mike Sullivan, both pitchers and Washington area residents, were selected as consecutive choices yesterday in the first round of the major-league baseball's free-agent draft.

Hammaker, who attended Alexandria's Mount Vernon High School and who just completed his junior year at East Tennessee State, was the 21st player picked, going to the Kansas City Royals. Sullivan was then selected by Cincinnati. He attended GarField High in Woodbridge, Va., and has just finished his third year at Clemson.

Seattle opened the draft by picking outfielder-first baseman Al Chambers of Harrisburg, Pa., an 18-year-old slugger who battled .484 and .434 in his final two years at Harrisburg High.

"Chambers has the most power of any free agent I've seen," said Mariner scout Bill Kearns. "In a few years, people will pay just to watch this guy taking batting practice."

Southpaw Hammaker and right-hander Sullivan pitched against each other when their college teams met three weeks ago. Sullivan earned the decision after Hammaker was removed and East Tennessee lost on a late error.

"A lot of scouts had told me to expect to be picked in the first three rounds, but no one told me it would be in the first," Sullivan said. "I walked in the door and found out about in when a Cincinnati newspaper called."

The 6-foot 170-pounder compiled a 10-0 record for the fifth-ranked Tigers, striking out 79 in 91 innings en route to a 1.98 ERA. Clemson lost to Miami of Florida in the NCAA regionals.

Hammaker, 6-2 and 193, was 6-3 this season with an earned-run average of 3.72. He fanned 89 batters im 77 1/3 innings. Hammaker won seven of eight games in his senior year at GarField.

Right-handed pitcher Tim Leary of UCLA was the second player selected, going to the New York Mets. He was one of 10 pitchers selected among the 26 first-rounders.

University of Michigan quarterback Rick Leach, who was a fifth-round choice of the Denver Broncos in the National Football League draft May 3, also was an outfielder of the Wolverines and was the 13th player drafted yesterday by Detroit.