Diarra took in a Real training session during his visit.
"The team is starting to build up their confidence again and there is a lot of energy and enthusiasm and a 'do it right' attitude. In my time at the club we beat them and they can do it too because individually-speaking, the quality of team is much higher than it was when I was there," said the Mali ace.
"(Jose) Mourinho is an excellent coach and he knows what has to be done. It's very difficult for a team led by Mourinho to be knocked out after a two-legged play-off. Home or away, Real Madrid always has a chance to score."