Baseball's gossip mill has been pumping out rumors that disgraced Yankees' ace Roger Clemens is considering suing Major League Baseball for his inclusion in the Mitchell Report. That was before Andy Pettitte, his close friend and Yankees and Astros teammate since 1999, admitted yesterday that he used human growth hormone, implying that the information disclosed Friday in George Mitchell's report on steroids was accurate. Trainer Brian McNamee told Mitchell that he injected Pettitte with human growth hormone on two to four occasions while the pitcher was rehabbing from an elbow injury at the Yankees' training facility in Tampa and that he repeatedly supplied and injected Clemens with steroids. Through his lawyer, Clemens vehemently denied using steroids and HGH. Attorneys close to the game say the rumors of a possible Clemens' lawsuit are most likely fueled by frustration and amount to little more than an empty threat from Clemens, especially now that Pettitte has confirmed the information contained in the report. Robert Kheel, a New York sports law attorney and Columbia University lecturer who has represented MLB in labor negotiations, said he doesn't believe Clemens has grounds to sue. "I do not know what specific evidence they may wish to assert," Kheel said. "But it would appear that a lawsuit would be without merit."