Robert Lewandowski has reminded Bayern Munich that they need to keep on top of their transfer plans in order keep the squad fresh as the current crop get older.

Although Bayern have shot to the top of the table thanks to four successive Bundesliga wins since Jupp Heynckes' appointment as head coach, it has by no means been a smooth start to the season for the Bavarians.

Bayern produced a number of lacklustre displays under Carlo Ancelotti prior to his sacking in the aftermath of a 3-0 defeat to Paris Saint-Germain in the Champions League, form that also cast doubt over the future of certain members of the squad.

Six members of Bayern's first team are 30 or older and Lewandowski believes that is something they must not lose sight of.

"We shouldn't delude ourselves," he told reporters. "Each club needs to get a top player every two or three years to refresh the team, to bring some new blood, new quality.

"At this point we really have a good team, but it is known that players are getting older.

"We are succeeding [at replacing older players] at the moment, because we have a young Joshua Kimmich, who is really good at his new position and shows that a young player can be a replacement for such an experienced and wonderful one as Philipp Lahm."