Paralympic and world champion Aled Sion Davies will miss London's Anniversary Games to have surgery for a hernia.
Davies is expected to be out for up to 12 weeks and the Welshman hopes to return in time for October's IPC World Championships in Doha.
The 24-year-old had been due to compete in the IPC Grand Prix final at the Olympic Stadium on Sunday, 26 July.
"I am naturally devastated not to be able to compete," Davies said.
"I was really looking forward to competing in front of another home crowd, who are always incredible.
"My focus now shifts to my recovery and rehabilitation to ensure I am back to full fitness as soon as possible."
Davies set a stadium record in winning the F42 shot put at the inaugural Anniversary Games in 2013 and also won the title 12 months later.
He will be denied the chance to defend his Paralympic F42 discus title after the event was cut from the Rio 2016 Games.
But the Bridgend-born athlete hopes to be fully fit to defend his world discus and shot put titles at the IPC World Championships in Doha in October.
"My aim is to be back in the throwing circle in time to be able to defend my two World Champion titles," Davies added.
"I have a great team around me and I have every confidence and faith that they will have me back to full fitness as quickly as they can."