Chelsea boss Thomas Tuchel said he substituted Callum Hudson-Odoi just 31 minutes after the winger came on in the 1-1 draw at Southampton because he was not happy with his attitude.
"Maybe it is even unfair, but it was my feeling," Tuchel said.
Talking to BT Sport, he added: "I was not happy with his attitude, energy and counter-pressing.
"I took him off and we demand 100%, I feel he is not in the right shape to help us. It was a hard decision but tomorrow it is forgotten and he has all possibilities to start against Atletico Madrid [in the Champions League on Tuesday]."
Tuchel added: "Everyone has to understand that I take decisions to win games and there is no problem that he makes mistakes and has a bad game, but we can't lack energy even 10% or 5%.
"He knows what I demand from him and when he doesn't reach this level, it's a hard decision."
"We not only had possession but good possession in the opponent half, in the last 20 metres we lacked quality and that is the truth," said Tuchel.
"We lacked determination, aggressiveness and more one on one chances. We controlled 80 metres, all counter attacks and when you control the match like this and you need a penalty to score, you see the problem is clear."
However, Saints manager Hasenhuttl was satisfied with a positive result in light of their recent torrid run.
"A draw feels like a win," he said. "It's a step towards us returning to our normal form."
"We are believing in what we are doing. The Premier League is tough. For us, it is good that we take a point from such a strong side."