Two defensive blunders proved costly for Glenavon as they went down to Shakhtyor Soligorsk of Belarus in their Europa League first qualifying round, first leg tie at Mourneview Park.
Mikhail Afanasiev slotted home in the second minute after a James McGrath mis-kick put his side under pressure.
Dmitri Komarovski ran through and shot low past McGrath after intercepting a pass to McGrath on the half hour.
Substitute Mark Patton fired into the roof of the net with four minutes left.
The visitors were gifted an early goal when McGrath's attempted clearance went astray. The home goalkeeper looked to have atoned for his blunder when he saved well from Nikolai Yanush, but the ball fell to Afanasiev, who found the net.
The hosts battled hard to bounce back from that early setback but Rhys Marshall shot tamely at Vladimir Bushma from a few yards out with the goal at his mercy.
Soon after, Conor Dillon headed narrowly wide from Andy Hall's free-kick, while Artem Starhorodskiy was just off-target with a shot.
Komarovski made it two when he pounced on Ciaran Martyn's error, collected the ball 10 yards inside Glenavon's half, and produced a composed finish.
The striker almost grabbed his second when he smashed an effort off the near post after Andy Kilmartin under-hit another attempted back-pass.
Kevin Braniff missed the target after meeting a pass from Eoin Bradley, but forced the visiting goalkeeper into a save later in the game.
Bradley turned and produced a wonderful chip which saw the keeper beaten, but Pavel Rybak lunged and managed to clear the ball off the line.
Patton met Bradley's cross to score a deserved goal for the Lurgan Blues and in the closing moments, Bradley crossed to the back post where Dillon was arriving, but a fine defensive header saw the ball go out for a corner.
"We gave it everything but two mistakes cost us a draw and possibly a win," said manager Hamilton after the match.
"The players are a bit rusty and they're going to make mistakes but they deserve great credit for the way they came back into the game."
The second leg will be played in Belarus on Thursday, 9 July.