Vincenzo Montella concedes he expects more from Leonardo Bonucci, but is backing the centre-back to raise his game at AC Milan.
Italy defender Bonucci was the biggest shock of an expensive transfer window for Milan after arriving from Serie A rivals and champions Juventus.
However, thus far Bonucci has struggled to make an impact and Milan find themselves in seventh after seven matches following back-to-back league defeats.
Montella, though, has no doubt that Bonucci will prove his worth to the team.
"Bonucci is fine physically and mentally, and we do expect more from him," he told a pre-match news conference ahead of Sunday's derby against Inter.
"I have no doubt about him. He is an important player, who has added to our value. I am convinced he will raise his game. At this moment, he is blamed for every small error, but he is strong and knows how it works.
"Leonardo is a player I will never regret signing. He is valuable for the present and the future."
Another close-season recruit that has struggled to bed in at San Siro is striker Andre Silva, who is set to deputise in the absence of the injured Nikola Kalinic against Inter.
Silva has just three league appearances to his name, but Montella was keen to talk up the 21-year-old's quality.
"He is a great player and scored nine goals in 10 World Cup qualifiers for Portugal," he said.
"I am sure he will make a mark in Italy. He has great quality."