"They knew each other, sent each other messages," the source claims. "It was flirtatious, but he never did anything with her."
Longoria, 35, filed for divorce on Wednesday, then accused Parker, 28, of sending hundreds of text messages to the woman.
Longoria didn't identify her, but the source says it was Erin Barry, wife of Brent Barry, who played with Parker on the San Antonio Spurs from 2004 to 2008.
Brent Barry's father tells TMZ the Barrys are also involved in a divorce.
Erin Barry couldn't be reached for comment.