Former AC Milan boss Fabio Capello says Leonardo Bonucci "can't defend" and was fortunate to play in a system that suited him at Juventus.
The Italy international moved to San Siro from the Serie A champions in a shock €42million deal but he has struggled badly for form during a difficult time for the Rossoneri.
Capello, who guided Milan to four Scudetti and the 1994 Champions League in a glittering spell in the early 1990s, has offered his own rather scathing assessment of Bonucci's qualities and the reason behind his poor performances.
"He's the best Italian defender when he has the ball at his feet. He's among the top three in the world," Capello told Sky Sport Italia.
"But he can't defend. He has big problems. It was ideal for him at Juventus, where he was free. It's perfect for him to play in a three [in defence]. Playing in a four is hard."
Bonucci has played in 16 of Milan's 18 Serie A matches this season.
Gennaro Gattuso's side, who face Inter in a Coppa Italia quarter-final on Wednesday, sit 11th in the league table.