The Wales international rejoined Liverpool in August after being told he did not feature in Mancini's plans. Bellamy shone for the club early in his City career but started to fall out of favour after the appointment of Mancini in December 2009.
However, Mancini said: "Bellamy is a good player. I am happy for him because he played very well. He is in good form. He was fit often but because we had three or four strikers it was difficult for him."
Bellamy spent last season on loan with npower Championship side Cardiff and later revealed how he and Mancini had differed in their opinions of his best training schedule. The 32-year-old has a long-standing knee problem which requires careful management.
He could now face his former club as the Barclays Premier League leaders travel to Anfield and he appears in good form after impressing in last week's win over Chelsea.
City have a poor recent record at Anfield having not won in their last eight visits. Mancini considers the 3-0 defeat there last April, when Andy Carroll struck twice, as one of the worst performances of his reign.
The Italian said: "It was poor, but it was one week before the FA Cup semi-final. We changed three or four players but Liverpool deserved to beat us."
This time City travel as impressive leaders of the Barclays Premier League having won 11 of their 12 matches, although they will be keen to recover from this week's Champions League setback. City were beaten 2-1 at Napoli on Tuesday to leave their chances of reaching the knockout stage out of their hands.
Mancini said: "We have started the Barclays Premier League very well but we know it will be a difficult game. The season will be very long. Every two or three games can change the situation.
"I hope we continue to win and continue to score. I am satisfied but I don't think we can win all the games. Everyone thinks we can win all the games but this is difficult."
Source: PA
Source: PA