The Catalan giants need to beat Bayern to ensure that they will qualify for the last-16 stage of the competition, although Xavi's team could lose and still go through if Benfica do not overcome Dynamo Kiev.
Fati has been sidelined since the start of the month, having picked up a hamstring problem in the 3-3 draw with Celta Vigo on November 6.
Barcelona had allegedly been hopeful of being able to call upon the 19-year-old for the clash at Allianz Arena, but Laporta has suggested that the Spain international is likely to miss out.
"It's something the doctors will have to decide, but I think it's complicated," Laporta told TV3.
Fati has scored 17 goals and registered six assists in 51 appearances for Barcelona in all competitions, including four goals in eight outings this term, having worked his way back from a knee issue. body check tags ::