Tsitsipas was injured in the French Open Final and received back treatment during the third set of the final. Despite the fact that he received back treatment and did play until the end. the injury must have been more serious than it appears to be initially and resulted in his withdrawal from the Halle tournament, where he was seeded as the number 2 player.
Federer is seeded as the number 5 player and yesterday struggled badly in the round 1 match against a qualifier. He won the match, but will meet much stronger opposition in Round 2. That is if he does not do what he did in the French Open and duck out of the series,