He didn't disappoint.
The 24-year-old from Vancouver scored a crucial straight-sets victory in the fifth and deciding match against Go Soeda as Canada beat Japan 3-2 to advance to the quarter-finals of the Davis Cup.
"It feels great. I'm not going to lie ... best feeling in the world right now," said a beaming Pospisil. "Pretty amazing, especially doing it here at home."
Pospisil won 7-5, 6-3, 6-4 in one hour 49 minutes after Japan staved off elimination in the World Group first-round tie when Kei Nishikori defeated Raonic in a five-set thriller earlier in the day.
"I've had so many ties where there was a chance to play the fifth match, but Milos always closed it out," said Pospisil. "Obviously you want to finish earlier, win earlier, but it was really special."
Pospisil, who is ranked 62nd in the world and has often played second fiddle during Raonic's meteoric rise into the top-10, lost to Nishikori on Friday before combining with Toronto's Daniel Nestor to win Saturday's doubles match to put Canada up 2-1 heading into the final day.
And after Raonic couldn't quite get the job done for Canada against the world No. 4, it was game on.
"It's a tough position. It's really tough. It's not easy," said Pospisil. "You start the first day against (Nishikori), then I had to play a crucial doubles match. You're not quite sure if you're going to play (Sunday). You're watching, you can't help it.
"You're trying to kind of ignore it as well and just prepare as best you can for your own match."
The decider itself was never really in doubt.
Pospisil broke the 86th-ranked Soeda — who was subbed in for Tatsuma Ito just before the match — while leading 6-5 in the first set to grab the lead in front of a flag-waving and hockey-jersey-wearing crowd on the lightning-fast court at the Doug Mitchell Thunderbird Sports Centre on the campus of the University of British Columbia.
Pospisil broke the Japanese again leading 4-3 in the second set before clinching the next point when Soeda's shot went long.
Soeda, 30, double faulted to put Pospisil up a break 2-1 in the third set before the Canadian sealed the next point with an ace to go up 3-1.
The pair held serve the rest of the way, and Pospisil closed things out with an ace before dropping to his knees to celebrate.
"There were few moments of fatigue, but honestly I had quite a bit in the tank still," said Pospisil, who finished with 14 aces to Soeda's three. "I was really focused on my service games and then pounced at the end of the sets."
Canadian captain Martin Laurendeau said depth in the squad was the key to victory.
"We've got Milos and Vasek and Daniel," said Laurendeau, whose team will meet Belgium in the quarters. "Those three guys can inflict a lot of damage indoors on a court like this in front of a home crowd."
With fans in a frenzy for what was viewed as the marquee matchup of the weekend, Raonic and Nishikori didn't disappoint in a back-and-forth affair that the latter eventually won 3-6, 6-3, 6-4, 2-6, 6-4 in three hours four minutes.
The turning point came when Raonic double faulted with the fifth set tied 4-4 to hand the point to Nishikori, who then clinched the match when the Canadian couldn't stretch far enough on a return.
The 24-year-old from Thornhill, Ont., fired 28 aces to the 25-year-old Nishikori's six, but it was that same serve that cost him at critical moments, especially in the second and third sets.
"Momentum, it changes around pretty quickly. I don't think I did anything wrong in (the fifth set). I think he just sort of buckled down later," said Raonic, who is ranked sixth in the world. "He played a few good points and that sort of decides it in that sense. The whole match, it comes down to one or two moments.
"I'm happy with the way I fought, I'm happy with the way I competed, and that's all I can ask of myself."
Canada made it to the Davis Cup semifinals for the first time in 2013, but lost to Japan in last year's first round with both Pospisil and Raonic out injured.
With a full complement of players this time around, Pospisil stepped up and delivered.
"It was a difficult position to be in and he handled it really well, like a veteran pro," said Laurendeau. "He trains and plays tennis for a situation like this. You want to score the winning goal in overtime in Stanley Cup playoffs, and as a tennis player you dream of a fifth point."