"It's going to be a tough match," Nadal said of his match against Raonic. "His serve is huge so I will need to return aggressively."
Raonic began his title defence with a 6-3, 6-2 win against Argentine Diego Schwartzman.
Better known for his groundstrokes, the Canadian came to the net 22 times, suggesting serve-volley specialist and former Wimbledon champion Richard Krajicek - who Raonic added to his coaching team last month - is already exerting an influence.
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But he lost 10 of those points, a rate of return he will want to improve on.
"I probably should have approached (the net) 12 more times and I probably should have won a few more," said the world number three.
"...I hesitated, but also, with him, you've got to understand that he's quite quick. So rarely do you get him sort of reaching for balls," added Raonic, who smashed 12 aces and won 75 per cent of his first-service points.
Former finalist Grigor Dimitrov beat French veteran Nicolas Mahut 6-2 6-4 to set up a quarter-final clash with Austria's Dominic Thiem who beat Australian wildcard Sam Groth 7-6(5), 6-3.
(Reporting by Amlan Chakraborty in New Delhi; editing by John Stonestreet)
