On a steamy, Pospicle-perfect day in Miami, Vasek Pospisil beats Juan Martin del Potro

There were a lot of warning signs for Canadian Vasek Pospisil as he took to the stadium court at the Miami Open Thursday to take on an opponent with a far more impressive resumé.

Other than a brief, one-tournament attempted comeback in Sydney in January, 2009 U.S. Open champion Juan Martin del Potro hadn't played in 13 months, and has had two surgeries on his left wrist (the latest just two months ago).

It was hot, and humid – conditions that Pospisil always struggles with. The opponent had major presence, along with a sizeable contingent of countrymen in the stands. It was a big match that had a lot of eyes on it.

But the 24-year-old from Vancouver came through, defeating del Potro 6-4, 7-6 (7) to advance to the second round.

Pospisil was down a break early in the second set. Del Potro served for the second set at 5-4 – only to break himself with two forehand errors and two double-faults. Del Potro also was up in the tiebreak.

But the Canadian hung tough, sticking to a game plan that was dictated by del Potro's frailty on the backhand side. His mighty forehand has always been the side to avoid but given the circumstances, this was even more true on Thursday.

He withstood a second-set surge from the Argentine, who pushed him back further in the court and started unleashing forehands as fast as 112 mph. But he kept pounding the del Potro backhand, which featured more one-handed slices than you would have ever seen in his healthy days. It opened up the forehand side, and Pospisil attacked.

Del Potro, at 6-foot-7, has never been the fleetest afoot. And though he has always put himself in position to hit as many forehands as possible, that was even more pronounced on Thursday as he basically camped on the left side of the court. The key was to execute and hit the opening, and Pospisil did.

Fresh off an impressive win last weekend in the doubles at Indian Wells with partner Jack Sock, and armed with a new career-best doubles ranking of No. 8, Pospisil will look to use that to make a good singles run, and get back into the top 50.

His next opponent will be an old friend, Bulgaria's Grigor Dimitrov, a year younger and the No. 9 seed.

The two go WAY back. Here's a Throwback Thursday homage to the 2007 U.S. Open juniors, where the two teamed up to get to the doubles final.

The 2007 Open was Pospisil's first-ever junior Grand Slam. He was already 17, so that didn't exactly scream "future star." Dimitrov, on the other hand, had that label early on.

The two lost to a French pair, Jonathan Eysseric and Jerôme Inzerillo, helped quite a bit in the second set by Dimitrov's immature behaviour. A penalty point in the latter stages of the second set quashed a comeback (there was racquet throwing, and ball firing, and all sorts of things).

The two had also reached the final of the big warm-up event just outside Montreal the previous week.

Dimitrov was a "big deal" then. Just 16, he would become the No. 1 junior in the world a year later, at that very event in New York, when he won the singles. He also won junior Wimbledon two months before.

He had the adidas sponsorship – as you can see from the pics above. Pospisil was wearing whatever he could pick up. And since the ITF mandated that doubles teams be dressed alike, Dimitrov lent him some gear.

Dimitrov's rise was a lot faster; only now is he finally getting away from comparisons to his style idol, Roger Federer. The former "Baby Fed" is around the top 10; Pospisil's rise has been slower. But he is the one who has a Grand Slam title in his pocket.

The matchup in the second round will be between two of the nice guys – two appealing players with equally appealing styles. The two have met twice in the pros; Dimitrov won both – in the qualifying at the Tokyo tournament in 2012 and at Federer's hometown tournament in Basel, Switzerland last fall.

This one could set up to be the best so far.