Bayern Munich goalkeeper and captain Manuel Neuer will miss Thursday's Champions League trip to Czech side Viktoria Plzen with a bruised shoulder, his club said.
The German champions will clinch a place in the last 16 with two games to spare should they win and Barcelona fail to beat Inter Milan at Camp Nou.
Sven Ulreich is expected to fill in for Neuer in goal. Thomas Mueller will take over as captain following his return from a Covid-19 infection.
Meanwhile, Barcelona coach Xavi Hernandez is searching for answers to that problem, with his team's form dipping at just the wrong moment, as they welcome Inter Milan and then face Real Madrid in the Clasico this week.
The Italian side visit Camp Nou on Thursday in a near life-or-death Champions League clash, before Barca visit the Santiago Bernabeu in a battle to move clear at the top of La Liga.
Coinciding with the team's struggles, reflected by a 1-0 defeat at Inter last week and a shaky 1-0 win over Celta Vigo on Sunday, has been Lewandowski's goal-rush drying up.