WHY ON EARTH WERE THIAGO SILVA AND ANGEL DI MARIA NOT SELECTED TO PLAY REAL MADRID.?

I really fail to understand the logic of the P.S.G manager in the champion league match played between Real Madrid and P.S.G. The P.S.G manager kept two of the very best players in the P.S.G club, sitting on the bench, and I ask what ever for? As the French giants P.S.G were playing the Spanish giants Real Madrid mind you not a small club like F.C.Basel, so P.S.G should have chosen their best players for this important match, you see he Spanish giants Real Madrid have won the champion league a total of 12 twelve times, the most by any club, and on the other hand P.S.G have not progressed beyond the quarter finals of the champion league, this was not the time to do any experiments on the pitch by changing players. But what I can not understand why ever should P.S.G keep their captain Thiago Silva and Angel Di Maria, who is in a goal scoring form, with even a tat trick recently sit out on the bench, this is madness and they got what they deserved a 3-1 thrashing, with no hope of a win in the second leg, for sure, unless of course unless Neyymar will dive and be given a penalty, that cheat he is.