Emotions high as Andy Roddick prepares for Juan Martin del Potro

He is not dawdling so much as lingering. Despite a chronically bad serving shoulder he refers to as "hamburger helper," regardless of being the lowest seed (20th) still alive in the U.S. Open men's draw, Andy Roddick has ramped up his game to extend his stay in what he has proclaimed to be his last professional tournament.

Tuesday night he will play a fourth-round match against Argentina's seventh-seeded Juan Martin del Potro, like Roddick a former Open champion -- Roddick in 2003, del Potro in 2009. Unlike Roddick, who estimates carrying physical and mental mileage beyond his 30 years, del Potro is in the prime of his career at 23.

With his surgically repaired wrist rehabilitated since his '09 title, del Potro must be considered the favorite. But Roddick, who has gone from the tennis A-Rod a decade ago to lovably sympathetic Raggedy Andy, has owned this year's event.

Even as top seeds Roger Federer and Novak Djokovic continue to advance almost effortlessly and No. 3 seed Andy Murray Monday night rendered a clinical 6-4, 6-4, 6-2 thrashing of 21-year-old Canadian Milos Raonic, Roddick holds on to the spotlight.

Murray, the gold medalist at last month's Olympics, virtually matched Raonic's rocket serve (138 mph to Raonic's 140) and repeatedly made Raonic hit the extra ball, often resulting in a Raonic error.

But enough of that Andy. When Roddick plays Tuesday night, "Love to see him go out and perform, play like he's capable, loose and free and serve big and have the crowd behind him," said Mike Bryan, who with his twin, Bob, has advanced to the quarterfinals in search of a fourth Open men's doubles title.

In the higher-profile singles, all U.S. men except Roddick have been grabbed by the back of the shirt and the seat of the trousers and tossed out of the party: Comeback player Brian Baker. Old pro James Blake. Young pups Ryan Harrison and Jack Sock. Long John Isner. NCAA champ Steve Johnson. And, on Monday by default, Mardy Fish.

"It's pretty fitting," Bob Bryan said, "that Andy, who has been the guy for so long, is the last guy standing. We're waiting for an American male player to take the torch."

Del Potro expects a "big atmosphere" Tuesday night; Roddick remains unsure of just how to navigate the situation. "I've been walking around with a smile on my face for three days," he said. "You're kind of smiling, humming, whistling, walking around and you feel pretty good.

"All of a sudden, you have to say goodbye to something. It's like this gut-check moment. It's these extreme emotions from five minutes to the next five minutes. You think you know what's going on, but I don't think there's any way to prepare yourself for it."

Asked after Sunday's victory about possible retirement advice he has received, Roddick addressed the Ashe Stadium crowd. "Anybody retired here? You want to tell me?"

Actually, they would prefer he linger.