Bruce said: "Towards the end we were game enough to keep trying but you could see a lot of tired bodies and the third game in six days was a bit too much for us.
"It was a big ask for us, we needed to be right at it and be fresh and it was a bit too much for us.
"A footballer can play a match every day but he can't play with the same intensity.
"We looked tired towards the end, your concentration goes and you don't have the energy to compete.
"Sometimes you have to say you were beaten by the better team and we were today.
"The disappointing thing is the game was settled by two set-pieces. Luis Suarez's free-kick has made the game comfortable for them in the end."