Nadal's first round encounter with compatriot David Ferrer ended prematurely after his opponent was forced to retire in the second set due to pain in his calf. Nadal had taken the first set 6-3 and was trailing 3-4 in the second before Ferrer called a halt to proceedings.
The defending champion did not face a break point during the first set but will have been frustrated by the fact he was broken twice in the second as he will no doubt be motivated to put down a marker at this early stage of the tournament.
Having lost just three matches all year on his way to five tournament wins, Nadal is in imperious form as he continues his quest to defend his US Open crown and add to his tally of 17 Grand Slam titles.
Pospisil enjoyed a straight-sets victory over Lukas Lacko on Monday to reach the second round at the US Open for the third time in his career.
The Canadian currently sits at 88th in the world rankings having been as high as 25th back in 2014 but he enjoyed some encouraging results on the Challenger Tour in the build-up to Flushing Meadows, reaching the semi-finals in Vancouver.
The 28-year-old plays attacking tennis and will need to have all of his attributes on show if he is to penetrate the formidable Nadal defence.
The fact that Nadal's first round slugfest with David Ferrer was cut short will only serve him well as it has allowed him to preserve vital energy in what have been punishing conditions so far in New York. Pospisil plays an attractive brand of tennis and he may have some joy on occasion with his big serve and forehand, but Nadal's defence should be more than equal to what the Canadian can throw at him over the course of the match so the world number one can look forward to a straight sets victory.