Milan coach Sinisa Mihajlovic says his players should have done better in today's early kick off away at Genoa.
The Rossoneri suffered their third defeat of the season as they failed to improve their position in the table.
Defender Alessio Romagnoli was sent off in the first half but the Serbian opted not to comment on the referee's decision.
"We could have and should have done better today," Mihajlovic said.
"We created several chances, but we weren't able to make them count. It's a shame, because with a win today we could have put ourselves in a good position in the league table.
"It's not good enough however that we only play well in one half of the match.
"I am not interested in commenting on the referee's decisions. We played better in the second half, but we weren't clinical enough and didn't take our chances. We needed to play with more fighting spirit today.
"We have never played De Jong as a centre back and so I had to make the logical decision. Bonaventura can do a good job in several positions. We will see based on each match where to play him.
"In the final 10-15 minutes we brought on a third striker, but it doesn't necessarily mean you become more dangerous in attack. I don't like to see the team hoof the ball forwards.
"If there is the chance to play the ball, we need to keep a hold of it. At times Diego Lopez kicked the ball up-field and I prefer to keep the ball on the deck and try and build from the back."