Both players have been battling injuries but are tipped to feature in the UEFA Europa League last 32 first leg clash in Scotland.
Mancini was unwilling to give too much away when asked about both players in his media conference on Thursday.
"Vidic has been out because he was injured after the game against Sassuolo. He's been training for five or six days now," he said.
"He may play, he may be a sub, but he is quite familiar with this type of football."
Asked whether Kovacic could start, Mancini said: "It's not really about whether it's a particular player's night, let's hope it's our night tomorrow.
"We've got good quality, as he has, and it's an important match."
Mancini is wary of Celtic, with the Scottish Premiership leaders having won seven straight matches heading into the clash.
And he praised Ronny Delia's men for their style of play.
"We know Celtic is a good team. They play football very well, they don't play classic long ball and they try to play on the pitch," Mancini said.
"I think it will be a very difficult match because they also have good players, good technical players."
