The Coach is back under pressure after a fifth loss in 11 Serie A rounds, four in the last five, interrupted only by Wednesday’s last-gasp 2-1 win over Torino.
“I am very disappointed,” De Boer told Mediaset Premium and Sky Sport Italia.
“We didn’t play the first half at all. In the second we expressed our real football, but I can’t understand why we seem unable to play the way we want to for more than 45 minutes. I did not see a team with the confidence to win challenges.
“In our analysis before the game, we talked about this. I don’t know why we played with no character from so many of the players. I was very angry during the half-time break.
“This is just an issue of mentality. We have a lot of quality, but can’t do much when we have the mentality I saw in the first half.
“When we have the ball, we need to play. In the second half we did, but in the first it was always long balls and bad decisions to pass it right back to them.
“We have a problem at this moment. I said to the team during the break that we had to change and it looked like another team in the second half.
“As we saw against Torino, Banega can do very well in that position. It’s a question of discipline and in my view the system is irrelevant. Our midfielders are very good with the ball at their feet and that’s how we need to play. Instead I keep seeing long balls and that is not our style. We want to create chances by playing the ball.”
Eder was visibly angry when substituted and refused to shake De Boer’s hand.
“He is a player who always wants to win and gives 100 per cent, but he had played a lot recently and I wanted fresh legs. He hadn’t done that badly, but I wanted to change something.”
Surprisingly, €29.5m summer signing Gabriel ‘Gabigol’ Barbosa was not even on the bench. What is the situation?
“He is a good player and his time will come, but for me he is not ready to play yet.”
Inevitably, De Boer was asked about the rumours on his imminent dismissal.
“I still have faith in the squad and we can change this very difficult moment. We have a lot of quality, but it’s not sufficient. We must always give 100 per cent to use that quality.
“We cannot accept the first half performance today. We’ve got to play the entire game at this intensity, not just after 20 or 45 minutes, or just against Juventus.
“You need to ask the club, as I am just doing my work and that’s all I can do right now.”