Deryck Whibley, who fronts Canadian rock band Sum 41, has defied doctor's orders and performed at a festival after being injured in a bar fight.
The star was treated in hospital for a slipped disc after being attacked by three people in Japan on Thursday.
"Despite doctor's instructions, he has decided to play today's show at Summersonic regardless," the band said.
The group went ahead with the sets at the twin festival sites in Osaka on Saturday and Tokyo on Sunday.
They have had six UK top 40 hits, including Fat Lip, In Too Deep and Still Waiting.
Whibley married pop star Avril Lavigne in 2006, but the couple split up last September.