Halle - Second-seeded Kei Nishikori has pulled out of the Gerry Weber Open with a rib injury.
Nishikori reached the second round and was due to face Florian Mayer on Wednesday but told organisers that he was unable to play.
Mayer advanced to the quarter-finals with a walkover.
Nishikori took a medical timeout during his first-round win over Lucas Pouille.