Offloaded to help Milan try to balance the books, the pair helped their new club to cruise to a 4-1 win over Dynamo Kiev while their former team mates were labouring to a dismal goalless draw at home to Anderlecht.
Coach Massimiliano Allegri, who also lost forward Antonio Cassano when Milan swapped him with Inter's Giampaolo Pazzini, appeared to be clutching at straws as he tried to put a brave face on a shocking performance.
"In the first half we made a lot of mistakes technically and in the second half we had four goal scoring chances," he told reporters.
"Of course you need goals to win games but we took a small step forward and I'm happy with what the players did."
Allegri has tried to remain upbeat while seeing his squad disbanded throughout the summer, although his team's formation did not help the situation.
With the other midfielder Nigel de Jong concentrating on a purely destructive role, the plan left a huge gap in the centre of Milan's midfield.
Milan had huge problems playing the ball out of defence, passes went astray and the San Siro became ever more restless.
De Jong, heralded by chief executive Adriano Galliani as the missing link in the Milan team when he was signed from Manchester City, did little more than pass the ball sideways against Anderlecht and in practice acted as a fifth defender.
In contrast, Anderlecht's midfield were slick and passed the ball crisply, although they had trouble converting their neat approach work into scoring chances.
Galliani has repeated that Milan had no option other than to sell Ibrahimovic and Silva as the club could no longer afford their wages.
Earlier this week, he told French media that Ibrahimovic had wanted to stay at Milan and the Swede was no longer speaking to him.
"At the end of last season he came to me with his agent Mino Raiola and I assured him that he would stay. But the board had some discussions and he was sold," said Galliani.
"Since he went to Paris, he hasn't spoken to me anymore. He is right though as I didn't keep my word."
While Milan have slashed their wage bill, they could also suffer a drop in income through plummeting gate receipts.
Milan fans stayed away in droves, with the San Siro only one-third full on Tuesday.
"The return of Montolivo, Pato and Robinho will take some pressure off players from whom I ask different things," said Allegri.
However, with Robinho's notorious inconsistency and tendency to hog the ball, and Pato's unfortunate tendency to get injured, the returning players seem unlikely to be able to solve the team's problems.