Abeg!!! What is Mourinho trying to say? Does that need an explanation? Is Cech is not a Chelsea goalkeeper? Why explaining when Cech features and not saying anything when Courtois plays?:
"Courtois played consecutive matches, against Liverpool, Manchester Cityand Aston Villa, games where he needed to be very focused. Every detail is so important, even when he doesn't touch the ball, the focus must be permanent and I think a goalkeeper can also be tired. The tiredness isn't just physical, it's also from your nervous system."
"Petr has been working really well and hard. In every training session I was getting the feeling his condition was magnificent. Tonight he was the best option for the team, also in terms of leadership. John Terrywas ill this morning and he was probably out of the game until the last minute, so I thought I needed Petr's personality and capacity to communicate at the back. The decision was good."
-Jose Mourinho;
source: Chelsea FC
Definitely, the two are best in EPL. But for me Cech has kept more clean sheets than Courtois!