He played in the National Basketball Association (NBA) for eight seasons and was a member of the New York Knicks' 1969–70 championship-winning team.

[5] A back-up on the 1969–70 Knicks, Stallworth was forced into action in Game 5 of the 1970 NBA Finals after Willis Reed was injured early.

He was assigned to cover Los Angeles Lakers star Wilt Chamberlain, and aided in holding him in check when on defense.

In a game that the Knicks won after trailing by 16, Stallworth made a reverse layup after driving to the basket on Chamberlain in the final minutes; Wayne Coffey, a New York Daily News journalist and writer called it "one of the single most dramatic moments of the season.

"[6] Stallworth was traded along with Mike Riordan and an undisclosed amount of cash to the Baltimore Bullets for Earl Monroe on November 11, 1971.