Alberto U M must have come up with a strategy before the match. Two nervous teams, this was going to be the match they had to win/couldn't lose to have a chance to stay with the Champions or go to the Europa League. So at the start Undiano called every foul, even when it wasn't one.
You can never be sure if it worked, that nothing really bad happened because of Undiano's strategy. But I think it did.
AZ were the better team until two players were substituted, from then on it wasn't a team anymore, just players running. Olympiakos stayed calm and were a lot less tired at the end of the match and could even have won.