Son Heung-min said South Korea had been given "a big wake-up call" after toiling into the Asian Cup knockout rounds with a madcap 3-3 draw against Malaysia on Thursday.
The Koreans conceded a 105th-minute equaliser against the world's 130th-ranked team in Doha to advance as Group E runners-up, avoiding a last-16 showdown with pre-tournament favourites Japan.
Instead they will play the winner of Group F, which Saudi Arabia currently lead ahead of Thailand.
Tottenham Hotspur forward Son said the Koreans would "be ready for any team" after being made to work hard in a group stage that also saw them draw with Jordan.
"When you go into a tournament there are no favourites – there are always underdogs that catch you out," said the skipper.
"It was a big wake-up call to make us even stronger going into the knockout stage."
Bahrain topped Group E and will face Japan after a 1-0 win over Jordan, who also went through to the last 16.
Jeong Woo-yeong gave the Koreans the lead in the 21st minute, only for Malaysia to come roaring back with two goals early in the second half from Faisal Halim and Arif Aiman, the latter from the spot.
Some of the Malaysian fans were in tears as they contemplated a famous win.
But Paris Saint-Germain's Lee Kang-in forced an equalising own goal from Malaysia's goalkeeper with a sublime free-kick in the 83rd minute to make it 2-2.
Son thought he had won it for the Koreans when he scored a penalty four minutes into injury time.
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