Ricardo Carvalho has claimed that Monaco must be at their best over 180 minutes to stand any chance of beating Valencia to a spot in the Champions League group stage.
Leonardo Jardim's men meet the La Liga side in the first leg of the qualifying tie at the Mestalla on Wednesday evening, and Carvalho is fully aware that Monaco will be punished for a below-par display.
"I know Valencia very well and they're a team who play well at home," the Portuguese centre-back told Marca.
"At this stage it's important to play two games at 100%. We can't go from 50% in one to 100% in another. You have to have two matches of a high level.
"Experience is important, but the young players have to show their best performance."
Monaco recorded a 7-1 aggregate success over Young Boys in the third qualifying round.
