Andy Roddick carved out a Hall of Fame tennis career, yet fans often wonder what his trophy case might have looked like had he not competed in the golden era of men's tennis. The former world No. 1 and 2003 US Open champion spent his prime battling the legendary quartet of Roger Federer, Rafael Nadal, Novak Djokovic, and Andy Murray.

While those four giants were his primary roadblocks, Roddick recently highlighted two other formidable opponents who gave him unique challenges: the relentless Lleyton Hewitt and the thunderous Juan Martin del Potro.

On the 'Served' podcast, Roddick was candid about his 7-7 career record against the fiery Australian Hewitt. "One of the most stressful players I’ll ever play," Roddick admitted. "He made you stay there mentally and physically every time. You knew he was not going away. You had to beat him; he was never gonna go away."

Roddick also paid tribute to Marat Safin, calling him perhaps the one player of their generation who matched the raw talent of the "Big Three," albeit with a different approach to the game.

But his most awe-struck praise was reserved for Juan Martin del Potro, the towering Argentine whose career was derailed by wrist injuries. "Del Potro? You want to talk about what could have been?" Roddick mused. "He is an animal. They didn’t want to play him. That wasn’t fun for them. He beat them." Roddick's reflection underscores the sheer power and potential of del Potro, a player whose fearsome forehand could disrupt even the greatest.

Roddick's honest take is a powerful reminder of the depth of competition during his era, where champions weren't just defined by the "Big Four," but by a host of other elite, uniquely challenging athletes.