But his 10 career wins over number one-ranked players are the most by any player never to hold the number one ranking - and further proof, Djokovic said, that del Potro is among the elite.
A focused Djokovic continued to apply pressure in the third set until Del Potro finally cracked on serve to fall behind 5-3, with the Serb closing out the match with a ferocious overhead victor.
As well as going level with Sampras on Sunday, a win for Djokovic would put him just three majors behind Nadal and six back from Federer who is six years older.
He missed last year´s tournament with an elbow injury which sent his career into a mini-crisis. He almost quit tennis in 2015, after four wrist surgeries that wouldn't let him regain the form that carried him past Roger Federer to win the 2009 U.S. Open.
"The worst moment was in 2015 when I was close to quitting because I couldn't find a way to fix my wrist problems", he said.
Djokovic though fought off the noise and Del Potro's challenging tennis to eventually take the second in the tiebreak.
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Djokovic sprinted into a 3-1 lead in the third set before a battling Del Potro clung on, hitting back for 3-3.
"He's my idol. Pete, I love you", Djokovic said".
"I had my opportunities during second and third set".
The Serbian tennis ace, now ranked 6th in the world, cruised through early rounds of the tournament and will enter the final with a 13-set winning streak, while on the other hand, Potro booked his berth after Rafael Nadal bowed out in the semis owning to his right knee injury. But even the straight-sets win had its moments, moments of vintage Djokovic: an on-the-line victor, an overhead smash, a passing shot, a backhand cracker. That prompted to chair umpire Alison Hughes to chastise them. The massive forehand and punishing serve of his early years remain, the two-handed backhand has begun to reappear, along with the slice backhand del Potro introduced to reduce the stress on his wrists. He finished with a flourish, taking the last three games. It all bothered Djokovic, who started yelling and gesturing toward the seats.
Djokovic said it was the kind of heavyweight clash he's learned to embrace.
The tiebreaker was resolved thanks to more del Potro miscues on his forehand side, as he looked more and more worn out. But then came another gruelling rally which showed just how tough an athlete, how determined a competitor, and how devastating a returner Novak Djokovic is. Pete, I love you. "Today I really am".