The clash between the European giants has been eagerly anticipated after Milan's Swedish striker Zlatan Ibrahimovic made disparaging comments about his former coach Guardiola in a recently published autobiography.
The news that Vilanova underwent surgery on his saliva glands as the team flew out to Italy dominated the pre-match build-up, though, the club saying the operation had been satisfactory and that he would be laid low for three to four weeks.
"I don't know how Tito is because the operation has only just finished but I hear it is positive news," Guardiola told a news conference.
"Tito is an extraordinary person and we hope he will soon be back with the squad again and able to get back to an ordinary life.
"[The impact on the squad] was similar to the news regarding Eric Abidal although they are different problems.
"We will go out and do what he has helped us to do in recent years but the most important thing is his health."
The European and Spanish champions were rocked last season when defender Abidal needed surgery to remove a liver tumour, though the French international was able to make a triumphant return to lift the Champions League trophy in May.
When Guardiola was asked about the meeting with his former striker Ibrahimovic, who left the Nou Camp under a cloud last year, he played it down.
"I don't have any kind of problem with Mister Ibrahimovic and I always believe you should act normally," Guardiola responded.
"If we meet, I will say hello like the sportsmen that we are."
Holders Barca top Group H two points ahead of Milan, the two clubs vying for top spot with two matches left to play.
