Inter Milan boss Frank de Boer says they "forgot to play football" in defeat to Cagliari.

The Nerazzurri had opened the scoring through Joao Mario, but were undone by Federico Melchiorri and a Samir Handanovic own goal.

“We had more spaces after going 1-0 up, but we simply forgot to play football," De Boer told Mediaset Premium.

“That was the problem today. The first half was pretty good and we put many crosses in, but we need to improve in the opposition penalty area."

Mauro Icardi also missed a penalty as his clash with ultras over comments in his autobiography reached fever pitch.

“I don't know what was going through Icardi's mind, but normally he is a player who remains very calm in these situations," added De Boer.

“We'll think about the incident tomorrow, as we work for the greater good and that means the fans too."