Real Madrid boss Carlo Ancelotti admits his players have been flagging in recent weeks.
Real appear to have blown their title hopes with some poor results.
Ancelotti said: "Our mental energy has failed us over the last two games and I can see the team are mentally tired.
"There is nothing wrong with their physical condition.
"It's not easy to recover your mental energy between Champions League semi-finals, and that energy is very important at that stage of the season."
