South Korea's World Cup preparations hit a stumbling block as they were beaten 3-1 by Bosnia and Herzegovina in a friendly on Friday.
Shin Tae-yong's men are playing four warm-up matches ahead of Russia 2018 but, after comfortably defeating Honduras last time out, Bosnia and Edin Visca had too much for them on his occasion.
Visca struck a brilliant hat-trick to seal victory, with Lee Jae-sung's first-half effort all South Korea had to show for their efforts as they continue to build towards their June 18 finals opener against Sweden.
After a slow start in Jeonju, where Edin Dzeko initially came closest to breaking the deadlock, the match burst into life with two goals in three minutes.
Bosnia struck first as Visca drilled past Kim Seung-gyu at his near post, but the hosts' response was immediate and Lee dinked a finish into the net following Hwang Hee-chan's cute lay-off.
Visca had his second on the stroke of half-time, though, when Haris Duljevic's glorious pass set the winger away to apply another devastating finish from a similar position on the right.
And the Bosnia man completed his treble in spectacular fashion with just over 10 minutes remaining, hammering a volley into the top-right corner from Rijad Bajic's cross.