"That's normal," Guardiola said of his striker's reaction to being replaced.
"The players want to play and I can understand him. He is a top player. But at that moment I needed a little more energy with Gabriel in that position. That is why I decided to take a decision.
"Always I don't want to hurt the players, believe me. Always I understand them because I was a football player and they want to play. But I have to take decisions.
"Before the game I thought the best option was Sergio and said to Gabriel I thought that. (If) he's sad and upset, I'm sorry but I'm just thinking about the next one.
"When the manager takes a decision and we win, always we are right. When you don't win, you make a mistake. So, it is simple like that."