Playing at Wimbledon on his 24th birthday, the Vancouver player saved three match points before falling to Robin Haase 7-6 (8-6), 4-6, 7-5, 6-3 on Monday.
Despite his loss, Pospisil was more than satisfied that the back pains which had made his life hell for the past six months have been fixed thanks to a diagnosis by a Prague doctor after months of uncertainty.
Pain-free over the last two weeks, Pospisil said he now knows exactly what was bothering him and that the problem has become "completely manageable."
Pospisil came to the All England Club after reaching the quarter-finals on grass last week in the Netherlands in his best career performance on the surface.
"This was the first match of the year which felt normal," said the player who began to be bothered by his back in Chennai in early January. "Last week was the first week of the season in which I recognized myself on court in terms of competing.
"I played quite well last week and today I just had a couple of mistakes and it didn't work out.
"But this was definitely a normal match. Now I can focus on what I need to work on. Not playing much probably cost me today. My main goal now is to stay healthy and finally be able to work on improving my game."
On the women's side, Aleksandra Wozniak of Blainville, Que., was also eliminated, losing 6-1, 6-2 to Dominika Cibulkova of Slovakia.
The No. 31 seed was beaten in a battle lasting one hour 38 minutes to leave his Wimbledon main draw record at a 2013 win and two defeats.
Pospisil hammered over 21 aces against Haase and produced 58 winners to 44 for his opponent, but he converted on only one of five break points.
The Canadian dropped the opening set in a tiebreaker and levelled by winning the second before Haase took the lead two sets to one as he broke in the final game of the third.
Haase earned another break for a 3-1 lead in the fourth set but was unable to close it out immediately as Pospisil salvaged three match points in the ninth game.
But a cross-court forehand winner gave Haase one more winning chance, which he took when Pospisil's volley went low into the net.
Pospisil and Haase and split two meetings last season with a win apiece.
Pospisil was one of three Canadian men in the singles draw, where eighth seed Milos Ranoic of Thornhill, Ont., heads the effort. Frank Dancevic of Niagara Falls, Ont., earned a lucky loser spot in the 128-man draw.