Bayern Munich coach Julian Nagelsmann will decide only shortly before the game which central defenders will face Barcelona striker Robert Lewandowski as he returns to Munich for their Champions League Group C match on Tuesday.
The Poland forward, who scored 344 goals for Bayern in 375 games during his eight years at the club, joined the Spanish side in July in a deal worth 45 million euros ($45.63 million).
The Bundesliga's second highest all-time scorer forced a move from Bayern despite having a contract until 2023.
He criticised the German champions who he said "tried to find an argument why they can sell me to another club because before it was difficult to explain maybe to the fans".
Bayern in turn said the situation had been caused by the player who asked to leave despite having a contract, before the two sides partially mended ties.
"I am certain on many positions but not the ones in central defence yet," Nagelsmann told a news conference.
He can choose between Dayot Upamecano, Matthijs de Ligt and Lucas Hernandez, with the latter having a slight advantage.
"Upa has more duels against Lewi in the Bundesliga (when the defender played for RB Leipzig). He always defended well against him but I have not decided yet," the coach said.
Nagelsmann said Lewandowski was still at a top level despite his 34 years and expected him to keep scoring an average of 40 goals a season. The striker has six LaLiga goals in five matches for Barca so far this season.
"He is their most dangerous threat in front of goal. I wish he can continue playing at this level for many years. If he maintains the physical fitness he can play for sure a few more seasons at this level.
"In the last few years he has been scoring about 40 goals a year. He is on a good road towards achieving that this season.
"We have to stop passes and crosses to him. But there are several other very good players in that team as well," Nagelsmann added.
Bayern, who beat Inter Milan 2-0 away in their Champions League group opener last week, have drawn their last three Bundesliga matches to drop to third place.
Saturday's 2-2 draw at home to VfB Stuttgart was bitter for Bayern who conceded a stoppage-time penalty equaliser.
