The game was evenly poised at half-time and United had their chances to go ahead early in the second-half.
But it was PSG who took their opportunities to claim a 3-1 victory.
"A disappointing night, football's a game of fine margins," Maguire said.
"We had the better chances, their goals were scrappy goals bu they've stuck it in the back of the net.
"We came away with nothing but I feel like we deserved something. You've got to be clinical, take your chances and not give them soft goals but they haven't opened us up with their talent. We've got to pick ourselves up, it's still in our control to go into the knock-out stages."