Lee Young-jun of South Korea celebrates his goal against Ecuador during the teams' round of 16 match at the FIFA U-20 World Cup at Santiago del Estero Stadium in Santiago del Estero, Argentina, on Thursday.(Yonhap)

When South Korea head coach Kim Eun-jung was preparing his players for the round of 16 match against Ecuador at the FIFA U-20 World Cup in Argentina, he delivered a straightforward message: that this could be their last match in the tournament and there's no tomorrow.

That sense of urgency paid off in South Korea's 3-2 victory in Santiago del Estero, northern Argentina, on Thursday, and South Korea will move on to take on Nigeria in the quarterfinals on Sunday, back in the same city.

"Our players were well prepared," Kim said after the victory at Santiago del Estero Stadium. "I told them that since we're in the knockout phase, we may not get to play another match after this and this could be our final day here. And they followed my instructions really well during our preparation."

Lee Young-jun and Bae Jun-ho scored a goal apiece within the first 20 minutes of the match. After Ecuador responded late in the first half, Choi Seok-hyun restored a two-goal lead for South Korea 2 1/2 minutes into the latter half.

Ecuador got back within one with an 84th-minute goal by Sebastian Gonzalez but couldn't get any closer.

"Ecuador played with a lot of confidence and their players gave our guys problems with their physicality," Kim said. "I want to thank my players for staying focused until the final whistle."

Bae was the offensive star, registering a goal and an assist. He was benched for South Korea's first group match against France with an adductor injury, and didn't look to be close to 100 percent when he started but was eventually subbed out in the next match against Honduras.

Bae was a second-half sub against Gambia in the final group stage match. And in his second start of the tournament, the 19-year-old midfielder for Daejeon Hana Citizen FC showed off his offensive chops.

He assisted on the opening goal by Lee with a pretty diagonal cross in the 11th minute. Bae then joined the party eight minutes later, when he fooled both the defender Daniel de la Cruz and goalkeeper Gilmar Napa with a nifty feint before scoring with his right foot.

"I'd felt bad about being hurt and not helping my teammates much," Bae said. "Rather than trying to play well, I just tried to play hard today. We'll try to keep this going and play another good match."

Kim refused to single out any particular player for praise, saying the victory was a total team effort.

"We battle and win as a team," Kim said. "Whether it's the guys in the starting lineup, those who came off the bench in the second half, and even injured players, we are always moving together as a team."

Kim said the team's collective mindset heading into the quarterfinals won't change.

"We will put all of our energy into preparing for Nigeria and we will prepare as though there won't be another match after that," the coach said. "They have one more day of rest than we do (after winning their round of 16 match Wednesday), and we will try to recover in time." (Yonhap)