Both players missed Saturday's 1-0 home win over Udinese, a result that was earned by Valter Birsa's superb 22nd-minute strike.
Balotelli returned from international duty with Italy carrying a thigh problem, despite making a substitute appearance and scoring in the 2-2 draw with Armenia, while Abbiati has a calf strain.
And Galliani does not rate either's chances of being involved in the Champions League encounter in midweek.
"From what our staff tell us, it will be very difficult for Balotelli and Abbiati to recover in time for Barcelona on Tuesday," he told reporters.
"I have total faith in ([taly national team doctor] professor Enrico Castellacci, so if Italy allowed him [Balotelli] to play then they must have been convinced he was fit.
"People say we have multiple muscular injuries, but that's not true.
"Only Balotelli and Abbiati are muscular, but most others were fractures and knee operations."
In light of Abbiati's injury, coach Massimiliano Allegri handed a senior debut to 21-year-old goalkeeper Gabriel against Udinese, and he responded with an assured display and a clean sheet.
"I chose Gabriel because I have a lot of faith in him," said Allegri.
"I evaluated he is not in the Champions League squad, as when we drew it up he had a shoulder injury, so Marco Amelia will have to play on Tuesday against Barcelona.
"Seeing as we get one injury after another, I tried not to risk Amelia. Gabriel has great qualities and is a great prospect for the future."