Gianluigi Donnarumma's mistake against Cagliari on Sunday was played down by coach Vincenzo Montella as transfer speculation continues to surround the goalkeeper.
Agent Mino Raiola suggested Donnarumma was open to discussing a new deal at San Siro, with his current deal set to expire in 2018, amid reports Milan could force the teenager to see out his contract in the reserves.
Donnarumma fumbled Joao Pedro's stoppage-time free-kick in the last game of the season, allowing defender Fabio Pisacane to tap home the winner in a 2-1 victory for Cagliari, but Montella defended his goalkeeper.
"Let's leave him alone, sometimes we are forced to make mistakes," Montella said. "These things happen.
"I won't comment on Raiola's words. Everyone does his own job, he is not the one to whom I need to explain my words.
"Apart from today, it has been a very positive season. We have given many players a better value. We have returned to Europe and lifted a trophy, so it was a positive season."
Speaking ahead of the Cagliari game, Milan's chief executive Marco Fassone said he believes Donnarumma will stay at the club, despite Manchester City's Pep Guardiola recently lavishing praise on the 18-year-old.
"Mino Raiola is one of the best agents, so I wouldn't criticise what he does," Fassone told Mediaset Premium. "Gigio is a pillar for us to build the team around next season. We told him that and we told his agent.
"We are clarifying the situation. When I look at Donnarumma, I see in his eyes the desire to remain. What we cannot do is wait around. We need to give Montella his squad, we want to know if we've got a goalkeeper coming to the end of his contract or not.
"Our timeframe is rather shorter than Raiola would like. I am sure we'll find a solution, but at the moment there are no meetings planned.
He added: "Leaving Donnarumma in the stands for a year? No club would do such a thing. We don't want a goalkeeper whose contract is running down. We'll make our evaluations and we need a Plan B in case things don't go the way we want.
"It's a plan we have not yet fully developed, because we are convinced our project is ideal for Gigio. We are ready to make sacrifices for him, but if the response is not positive, then we'll look to Plan B."
Montella's future is also unclear with Milan's new owner Chinese businessman Yonghong Li reportedly considering a change in the dugout, but the coach shrugged off the continued speculation about his position.
"I am calm. I trust the management and I don't have anxiety," Montella said. "I'll give my technical assessments, I am in constant contacts with [sporting director Massimiliano] Mirabelli, we have a great relationship.
"We are considering the potential departing players and who could arrive at Milan. We had a zero cost transfer market, we didn't spend any money in January. Now the market operations will be done. The ownership have great ideas and great will to construct a better team."