He said: "The situation is the same wherever you manage. In Valencia if I decided to change a few players and we won people would talk about what a fantastic tactical move it was, but if you lose then it is because the manager made a mistake. That is okay, I accept the responsibility, but I also need to see the bigger picture and we have three games in eight days so we need to make changes.
"Had we scored in the first half against Everton it would have been a different game and we still would have had Xabi Alonso with fresh legs for the other games. If you lose it is because of a mistake but that is football. There is nothing wrong with Xabi, he is a fantastic player and professional, as you will find out against Portsmouth. I am sure he will do very well for us this season because he is a good professional, a good player and is training very hard.
"When we decide to change we analyse every player and every situation. Afterwards, depending on the result, people might think it was a mistake, perhaps it was, but that is part of football.
"We decide these things for the good of the team and the best time to judge whether it was a mistake to change players or not is at the end of the season."