Mancini's side face the Hoops at Parkhead tomorrow night in the first leg of a last-32 clash.
The Italian manager personally knows a handful of Celtic boys after working with Scott Sinclair, Olivier Ntcham and Boyata at Manchester City.
Ntcham, who was 17 when Mancini left, never played during that era, but the other two were highly-rated prospects at Eastlands at the time.
Sinclair will be available for a reunion, but the Belgian defender has been ruled out through injury, and the 53-year-old admits he is sorry that Boyata won't be around.
“I’m sorry Boyata won’t play but they have many excellent players. They’ve had a few injuries recently – but for a club like Celtic this will not affect them," he told The Daily Record.
“We’ll have a difficult match despite their injuries. It won’t affect the intensity of their game.”
Celtic fans probably won't share Mancini's disappointment. Reason being, Boyata has been a disaster in recent months and although the same applies to other Bhoys - most notably Jozo Simunovic - you get the impression that the 27-year-old would have struggled in a big way.