The holding midfielder has stressed that the Portugal star will be vital for his side in the second leg of the semi-final tie against Dortmund
The Spanish champions were beaten 4-1 in the first leg at the Signal Iduna Park last week and Khedira realises that they need the Portuguese to be in top form in the return if they are to have a chance of turning things around at the Santiago Bernabeu.
"Everyone who knows Cristiano realises that he is always geared up for every game, no matter if it is a decisive one or a game where there isn't much at stake," he was quoted as saying on the club's official website.
"He is a great professional, like all his team-mates, but we are going to need him and his goals more than ever on Tuesday.
"We all hope we can put in a good team performance."
Ronaldo has been in sublime form so far this Champions League campaign, netting 12 goals in 11 appearances.
Tuesday's encounter at the Bernabeu is scheduled to kick off at 20:45CET.