Ki Sung-yueng has wrapped up his English Premier League season early due to injury and returned to Korea to prepare for the upcoming World Cup. He arrived at Incheon International Airport on Tuesday afternoon.
The forward played for Sunderland this season on loan from Swansea but missed the club's last four games due to an inflamed knee ligament.
"I've been in quite a bit of pain for a long time, but it got worse as I kept on playing," he said. "I can't even jog at the moment."
His excessive workload this season may have worsened his condition. Ki was a key player in midfield for Sunderland, playing at 14 games from December to January. He scored four goals in 37 games throughout the season.
"I was struggling with the pain, with no sign of recovering despite three weeks of treatment in England. The team and I discussed the issue and they allowed me to make an early return to Korea," said Ki. "I want to make sure I get the proper rehabilitation so I can play an important role in the upcoming World Cup."
Four overseas players have now returned to Korea before the end of the season. Park Chu-young, who played for Watford on loan from Arsenal, came home in early April after being struck down with cellulitis. His injury is now fully healed, and Park is working on regaining his top form.
Park Joo-ho, who plays for Mainz 05 in Germany's Bundesliga, also had to end the season early due to cellulitis. Park Jong-woo of Guangzhou R&F in the Chinese Super League returned to Korea last week due to a thigh injury.
The final 23-man roster for the 2014 World Cup in Brazil will be announced on Thursday, and the national team will begin training from May 12.