Still nimble a month before her 50th birthday, Martina Navratilova extended her Grand Slam career for at least another match Thursday night. Hours after losing in women’s doubles, she teamed with Bob Bryan to beat Anna-Lena Groenefeld and Frantisek Cermak 6-3, 6-4 and reach the mixed doubles semifinals.

There was a quick wave from Lindsay Davenport as she walked off the court, her 16th U.S. Open over. No last look around the stadium. No on-court interview. No opportunity for a prolonged “Thank you and goodbye” from the fans of the sort lavished on Andre Agassi. Then again, who’s to say how many more U.S.

Italian tennis player Giulia Casoni tested positive for a banned substance and has been suspended pending an inquiry into the case. Casoni tested positive for Formoterolo — a stimulant used in asthma treatment — at a tournament in the Adriatic resort of Pesaro on July 28, the Italian Olympic Committee (CONI) said Wednesday.

Kim Clijsters of Belgium will miss the Fed Cup final against Italy because of a lingering wrist injury. Justine Henin-Hardenne will play for host Belgium with Kirsten Flipkens, Caroline Maes and Leslie Butkiewicz on Sept. 16-17, the International Tennis Federation announced Wednesday. Italy will be represented by Francesca Schiavone, Flavia Pennetta, Mara Santangelo and Roberta Vinci.

Win or lose, Andy Roddick, James Blake and Bob and Mike Bryan form a tight-knit group, the sort of camaraderie the U.S. Davis Cup team hadn’t enjoyed in quite some time. Now the big question is whether that friendly foursome can pull off a victory over host Russia in the Davis Cup semifinals Sept. 22-24.

A few days ago, Benjamin Becker wandered into Arthur Ashe Stadium, hoping to watch a match. The guards kicked him out. He didn’t have a ticket. Besides, they didn’t recognize him — hardly anyone outside the tennis world did, actually. That changed Sunday. The 25-year-old German who rarely makes it through a day without being asked if he’s related to Boris Becker — he’s not, never even met him –…