Pep Guardiola's side visit Estadio do Dragao for the quarter-final first leg with a number of key players on the sidelines and having played with just four men on the bench against Eintracht Frankfurt on Saturday.
Medhi Benatia is on the sidelines with a hamstring injury, while Arjen Robben (stomach) and David Alaba and Javi Martinez (both knee) are also unavailable.
Ribery, who has been struggling with an ankle problem, had resumed light training prior to the 3-0 win over Eintracht, but is still not fit enough to feature.
Vice-captain Schweinsteiger, meanwhile, is out because of a virus, although Jerome Boateng is available following muscular problems and Claudio Pizzaro is also included in the squad.
"Bastian and Franck cannot travel, that's too bad," Sammer said.
"We have complete faith in the players that we have available. Everyone knows the situation. The team have a real hunger."
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