Sinisa Mihajlovic feels Rodrigo Ely's red card sparked the downfall of AC Milan in their 2-0 defeat to Fiorentina in Sunday's Serie A opener.
The defender was shown two yellow cards in the first half of the new coach's maiden league game in charge, with the Viola subsequently firing two past the visitors.
Mihajlovic has admitted that his side were second best in the encounter, but feels they could have got something out of it had Ely not been dismissed.
"Until the sending off, the game was balanced, then things went bad," he told Mediaset. "Fiorentina were great in possession and things became difficult for us.
"They deserved to win while we did not do well in the midfield. Then we were outnumbered and it was impossible to recover.
"We knew it would be difficult to come to Florence. The red card and the goal that followed ended the game.
"We lost the match in midfield. We will work on this, we must definitely improve."
However, the coach did admit that the big changes the club have made over the summer means they cannot expect instant success.
"We changed the playing system and we have different players, but we had to do better, definitely."
Milan are in negotiations with Liverpool over a loan deal for Mario Balotelli, but Mihajlovic refused to comment on the prospect of signing the striker.
"I have not met with Mario," he said. "The club know what I need for my game."