Pierre-Emerick Aubameyang's negative body language was behind Thomas Tuchel's deicision to remove the striker from Tuesday's 1-0 Champions League defeat at Benfica, the Borussia Dortmund coach said.
Aubameyang put in a nightmarish performance in Portugal, missing two clear-cut chances at goal before sending a penalty directly at Benfica keeper Ederson.
Tuchel replaced Aubameyang with Andre Schurrle in the 62nd minute, with the coach saying he was not satisfied by his striker's reaction.
"Aubameyang is not fully fit after the African Nations Cup," Tuchel said. "His body language did not suggest that he would do better after giving away the penalty.
"I don't think he had a problem with the substitution."
Despite the defeat, Tuchel said he was encouraged that Dortmund could overcome the slim deficit and advance to the quarterfinals.
"It is an extremely complicated result, but I am very proud of how we played tonight," he said. "Even though I am very disappointed, I am proud of how we presented ourselves.
"I don't think we played well, I think we played outstandingly. That's only possible in football, to play this well and to still lose. Luckily, there's a return leg for such games.
"They attacked us differently after the break, we were not prepared for how they attacked our back three. Had we played two long balls in those situations, nothing would have happened."
Schurrle was also optimistic that Dortmund would be able to convert their many chances at the Westfalenstadion.
"I think we played better, especially in the first half, we had the better opportunities," Schurrle said. "Especially with the penalty, we should have won.
"There is a return leg and we will show that we were clearly better then and go through. We were clear through on goal and things didn't work out. Such days happen."
Julian Weigl said Dortmund should not only have won the game, but should have triumphed by a comfortable scoreline.
"We should have and could have taken more from this game," he said. "We put in a top performance, we created many chances. We had to win 2-0, 3-1 tonight.
"A 1-0 defeat is not the best position for the return leg, but we play in our stadium and it is still possible. But it hurts.
"I was fully convinced that one of our chances would go in, we absolutely would have deserved it. I don't quite know what to say, it's really annoying."