Right now it is a 4-1-4-1 system Pep is using. One holding midfielder - Schweinsteiger. Martinez will probably move into the defense.
Then you have Götze, Kroos, Müller, Ribery, Thiago, Robben, Shaqiri for the offensive four behind a striker or false 9. Seven for four.
Shaqiri right now still ain't the same class as the others - he probably still can live being a substitute. Six for four.
Götze will not start training until end of July - until he really is in the team it will be end of August - right in time for Robben's usual prewinterinjury. Five for four.
So that leaves Götze/Robben, Müller, Ribery, Thiago and Kroos for 4 spots. If you take Müller or Götze as real and/or false 9 there is even place for all of them...
There is a solution for everything.
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Actually the one person more with Götze even in a 4-2-3-1 usually should not have been a problem. Yes, somebody always has to sit on the bench, but it would have worked last year, too, if Heynckes would have distributed it fair with Ribery, Robben, Müller and Kroos. But at the beginning he never really had to - there was always somebody having minor injuries, colds and then Robben had his usual injury until the winter break. But actually it would not have been bad if especially Ribery and Müller would have gotten more rests in that time especially in November - as a result they were pretty spent in the last weeks before Xmas.
When Guardiola changes the system like he seems to want to - there is one place more for them. With Gomez leaving and Mandzukic and Pizarro being the only strikers - there is another additional spot for Müller or a false nine with Götze. As long as you have Müller in the offensive midfield you always have the option for a part time real striker in addition to a false nine project.
And there always will be an injury of somebody. An injury of Robben just is pretty normal. Ribery has been off bigger injuries for the last two years but sometimes he misses a match or two out of precaution - but that might just be luck as he has had more injury problems before that (but he lives more professional now and is very cautious). Kroos missed some months in 10/11 and again in 12/13. Götze for a young player has a lot injuries - maybe it helps that it is no need for him to play all matches anymore. Müller's biggest injury or sick period he had since playing for Bayern as a ten year old took him out one week - but there is never a guarantee.