Pospisil was a 6-3, 6-4 winner over No. 9-seeded Richard Gasquet. Pospisil was good on less than half of his first serves but still didn't face a break point and lost only 16 points over 10 games serving.
Gasquet dropped only 15 points in his nine service games but Pospisil converted both break chances he had and advanced.
Paire topped 13th-seeded Gilles Simon 6-4, 6-3, taking 70 percent of the points on serve and winning three of his four break-point opportunities.
No. 10-seeded Milos Raonic also fought off three break points in a 6-4, 6-4 win over Michal Przysiezny in winning his first-round match. No. 12-seeded Kei Nishikori defeated Grigor Dimitrov 6-3, 6-4 while 15th-seeded Nicolas Almagro, behind a 16-ace attack, beat Go Soeda 7-6 (7-5), 6-2 and No. 16-seeded Tommy Robredo was on the court 56 minutes in a 6-4, 6-1 win over Albert Montanes.
Fabio Fognini rallied for a 4-6, 7-6 (7-5), 6-4 decision over Paolo Lorenzi in a 2 1/2-hour match. Jurgen Melzer also came from a set down in beating Ivan Dodig 4-6, 6-3, 6-4.
Other unseeded players headed to the second round with wins Tuesday are Andreas Seppi, Philipp Kohlschreiber, Daniel Brands, Jeremy Chardy, Feliciano Lopez, Kevin Anderson, Fernando Verdasco and Alexandr Dolgopolov.