However, their task has been made all the more difficult with the news that Ki will miss the must-win match against the Germans in Kazan after picking up a calf injury in Saturday's 2-1 loss to Mexico.
"A medical inspection at a hospital showed that Ki damaged his left calf muscle," Yonhap News quoted a national team official as saying on Sunday. "He needs two weeks of treatment."
Ki left the Rostov Arena on crutches, the report said.
Yonhap also quoted a Korea Football Association (KFA) official as saying they would submit a letter of complaint to world soccer's governing body FIFA over an incident in the build-up to Mexico's second goal on Saturday.
Referee Milorad Mazic chose not to penalise Hector Herrera for a dubious tackle on Ki that allowed the Mexicans to break on a sweeping counterattack which Javier Hernandez finished off to make it 2-0.
The KFA official questioned why the Video Assistant Referee (VAR) system was not used to review the incident, which South Korea coach Shin Tae-yong described as "100 percent a foul".
"There's a zero percent of chance that the call will be reversed," the KFA official added.
"We just want to express our regrets and make sure that this kind of incident never happens again in our next match."
(Writing by Peter Rutherford in Seoul; Editing by Greg Stutchbury)
