A question mark heading into Miami, Milos Raonic already through to the fourth round

Canadian Milos Raonic needs only to defeat Damir Dzumhur of Bosnia on Tuesday to reach the quarter-finals of the Miami Open.

That's a pretty good deal, and it reflects the way both the men's and women's draws have been decimated by upsets and retirements over the last week or so.

The 25-year-old was uncertain of his participation in the second of two Masters 1000-level tournaments in the U.S., after the adductor problem that has limited his play this season appeared to pop up again in the Indian Wells final against Novak Djokovic. But he made the trip, and after a pair of tight straight-sets victories over American Denis Kudla and Jack Sock, he has the No. 94 ranked player in the world between himself and the final eight.

Raonic improved his head-to-head record with Sock, the No. 22 seed, to 7-1 with a 7-6 (3), 6-4 victory Monday night that could easily have turned late in the second set, when the American began handling Raonic's second serve a little more effectively and made a charge.

Sock had a break point at 3-4 in the second set to get back on serve, and completely shanked a backhand, a turn of events about which he could only laugh. He had three more chances in that game but each time, Raonic rebuffed him. The game lasted more than nine minutes before Raonic was able to hold.

Sock saved a couple of match points, but not a third as Raonic, who had been limited to four aces in the first set, picked it up in the second with eight more and finished it off with a 140-mph delivery that Sock couldn't handle.

In the end, Sock's stat sheet was littered with unforced errors and his body language, particularly in the first set, was negative – no doubt due to the one-sided nature of their rivalry. He essentially gave away set point in the first-set tiebreaker with a premature, half-hearted attempt at a drop shot.

Sock has many of the tools Raonic possesses; a huge serve (their average speeds on both first and second serves were nearly identical) and a howitzer of a forehand that's unlike any other on Tour, rivaling Rafael Nadal with the level of its spin and topping it in terms of pure velocity. He has surprisingly good touch at the net, as well, as evidenced by his doubles success with Raonic's Davis Cup teammate Vasek Pospisil. But he doesn't use it nearly enough.

Mostly, though, he can't match Raonic for seriousness and intensity and in the end, it was that calm that helped Raonic to get through.

The Canadian is in the bottom half of the Miami draw, i.e., the non-Djokovic half. Among the seeds to have already fallen in his half: No. 2 Andy Murray, No. 4 Stan Wawrinka and No. 5 Nadal.

He will face Dzumhur for the first time.

"I know he fights hard, and has very quick feet, so expect a lot of balls back. But I feel the most important thing will be to dictate the centre of the court," Raonic said.

If Raonic gets through Dzumhur, he could face Nick Kyrgios of Australia in the quarter-finals, an opponent he knows well. If he gets through that, a potential semi-final foe could be Kei Nishikori of Japan, another opponent he knows well.

He said he's feeling okay.