Barca is in first place in the group and beat Inter 2-0 last time out without Messi.
Coach Ernesto Valverde said on Friday he did not rule Messi out of playing against Inter, but said he was concerned about rushing the player back, especially as his side are on a winning run without their usual talisman. "We're seeing them create very little but be efficient with the chances the do have".
"With Messi, Barca's degree of unpredictability increases but their attitude is the same without him", he said. "We have won without him but we're happy to have him with the group".
Guardiola parted ways with Messi and Barcelona in 2012, and went on to manage Bayern Munich before guiding the Sky Blues to the Premier League throne last season.
"We've always said we can play against anyone, and that still holds true". We Argentines do not realise what Leo represents for the whole world.
He only returned to training on Wednesday and did not feature in Saturday's 3-2 LaLiga victory at Rayo Vallecano but Barcelona have named him among their outfield options for a key clash at San Siro.
"This is a club where there is a lot to do".
"Inter came from a stage of difficulties but with the arrival of Suning, everything was restructured". I work on the key projects in the brand evaluation, social impact and worldwide relations that have helped the club a lot.