Mourinho hooked Diarra early as Rayo threatened.
He explained, "It pained me to change tactics in the first half. It's tough for a coach to replace a player on the 25-minute mark, but the team needed it. Lassana already understood the team is more important and that team objectives are paramount. We needed a second playmaker.
"Kaka and Ozil played closer to the goal. We didn't have a true number '10' on the pitch, but there were three excellent playmakers out there. We started pulling off more efforts. It's a shame I had to replace Kaka when we were down to ten men because he was giving a very good performance.
"Kaka and Ozil have to be prepared both physically and mentally to adapt to play closer to midfield. It isn't easy for them to do this for 90 minutes. It's risky. They have to be fit and aware that Xabi Alonso can't play alone in midfield for 90 minutes. They both responded very well. They created ball movement and covered Rayo's exits. They played well. It was a situation of risk but they transformed it into a positive scenario for the team."