Michael Lang struck late to deny Manchester United a 100 per cent record in their Champions League group after Anthony Martial and Marcos Roho hit the frame of the goal for United.
The shock defeat means the Red Devils are yet to secure top spot and now need to avoid defeat in the final fixture against CSKA Moscow in order to progress.
"We played against a team that played with five defenders," Mourinho said. "We knew that. We tried to play with three attacking players and that worked in the first half because they couldn't handle us."
United appeared to be caught in two minds about whether to hold on for a draw to secure qualification or push forward in a bid to win the game.
"We didn't score in the second half probably [because of] the fact that we know one point is enough," Mourinho added. "Probably [when] at 75 minutes, 80 minutes we didn't score, so it is not time to try to win, it is now time to try control and in the end we lost."
"So it's hard for me to be upset with the players. The first half the attitude was good, the football was good. It is really difficult to blame. It's just football," Mourinho concluded.