The Rossoneri defender was unimpressed once more, and has conceded that the club are currently vulnerable, with Pato insisting that he wants to do well for the club upon his return
The Rossoneri were once more undone as Lazio raced into a 3-0 lead at Olimpico on Saturday, with Nigel de Jong and Stephan El Shaarawy scoring to reduce the deficit to 3-2, though the visitors were unable to complete the comeback.
The defeat has also meant that for only the third time in Milan's history - and the first time in 70 years - the club have lost five times in their first eight games of the season, with Bonera suggesting the change of tactics by coach Massimiliano Allegri did little to help their cause against the Biancocelesti.
"We found [we were] playing solid with two midfielders, but tonight the coach decided to deploy De Jong in front of the defence with two players more offensive in [Antonio] Nocerino and [Riccardo] Montolivo," Bonera was quoted as saying by La Gazzetta dello Sport.
"At the moment we are a bit fragile even in form, as well as mentally."
Meanwhile, striker Alexandre Pato remained positive, having made his first Serie A appearance of the season, coming on for Nocerino in the 51st minute.
"Now I just have to play as much as possible because I miss the pace [of the match]. The team is growing, Milan will always be a successful club," he said.
"PSG? I still have a year and a half [left on my] contract, I just [want] to do well here. Guardiola? As everyone knows, he is one of the best, but at this time we think of our game and our boss."
Milan resume their Champions League campaign against Malaga in midweek.