AC Milan head coach Massimiliano Allegri is confident his side will overcome an injury list akin to a "wartime news bulletin" and raise their game for Champions League opponents Celtic.
Kaka joined the long list of players who will miss the San Siro encounter on Wednesday night when he was diagnosed with a adductor muscle tear on Monday after going off against Torino on Saturday.
Milan came back to avoid a second defeat in three Serie A games thanks to Mario Balotelli's penalty, which made it 2-2 with the last kick of the ball.
But the point came at a cost with Kaka, captain Riccardo Montolivo and fellow midfielder Andrea Poli all suffering injuries that rule them out of the Group H opener.
Forwards Stephan El Shaarawy and Giampaolo Pazzini are also out along with defenders Ignazio Abate, Mattia De Sciglio, Matias Silvestre and Daniele Bonera.
Quoted on his club's official website, Allegri told the media: "We didn't play well on Saturday, actually, we played very badly against a Torino side that caused us a lot of problems.
"Tomorrow will be a different game as they always are in the Champions League. It's a great atmosphere. The start of the group stages.
"It's a big match as we'll be up against a team that are very physically strong as well as being technically good players, especially in the attacking department. They'll be a tough team to face.
"I think that the players will put in a good performance tomorrow to put the match in Torino behind us.
"We're playing at home as well so we'll have our fans behind us as well just as they were in the match against PSV (when Milan won 3-0).
"There are all the ingredients for a great match and a great performance. I'm not worried at all about the situation.
"This period that we're going through, we've actually been a bit unlucky. The number of injuries we have reads like a wartime news bulletin but nevertheless, the work done by the medical staff and the physiotherapists has been outstanding."
While Celtic will be relieved not to face Kaka, whose goal knocked them out of the last 16 in 2007, they will come up against a striker who helped put them to the sword at the same stage last season.
Alessandro Matri scored in both legs of Celtic's 5-0 aggregate defeat by Juventus before moving to the San Siro in the summer.
Matri said: "It'll be an emotional night. My Champions League debut in the San Siro. I can't wait to get on the pitch and play this game.
"I played well against them last season so maybe that's a good sign and let's hope it happens again.
"Celtic are a tough team but they're not just physical. It'll be up to us to start the match on the right track and the fans will be a big help. "
Allegri revealed Matri would start up front alongside Balotelli with either Robinho or Slovenia international Valter Birsa playing off them.
Holland international Nigel De Jong will play alongside former Portsmouth player Sulley Muntari and Italy international Antonio Nocerino in midfield.
Meanwhile, AC Milan vice-president revealed Kaka was in tears when the recent signing from Real Madrid offered to forego his wages until he had recovered from injury.
"Kaka's decision came about during a phone call that I received from him where he was crying," Galliani told www.acmilan.com.
"He told me he wanted to feel the affection of Milan and to repay the fans for their support.
"He said he did not want a single euro until he returns to play.
"This act is evidence of the extraordinary rapport that Kaka has with the fans."