South Korea's 1-0 victory over Jordan in the Asian Olympic qualifying tournament Saturday in Doha exposed potentially disastrous defensive problems that could cost them a chance to compete in this year's Summer Games.

Midfielder Moon Chang-jin scored the lone goal in the 23rd minute of the quarterfinals at the Asian Football Confederation

U-23 Championship, which doubles as the Olympic qualifying event. South Korea were mostly in control in the opening half, but in the second half, they turned into an entirely different side and became too careless in their own end.

Some shoddy passing game and poor positioning on defense allowed Jordan to mount a ferocious charge, and they dominated the ball over the final 45 minutes.

If not for a borderline offside call, canceling out a nifty header by Baha' Faisal in the 67th, the match could have stretched into extra time or could have ended in a Jordan victory in regulation, considering how the momentum had swung in their favor over the final stretch.

South Korea did suffer some defensive lapses in two test matches prior to the tournament, and also in stretches during group play. The two goals that South Korea allowed in group stage -- one each against Uzbekistan and Iraq -- were both results of poor positioning by inexperienced backs.

On Saturday, problems ran much deeper. The defensive corps and the midfielders looked out of sync and gave away too much space to aggressive Jordanian attackers. South Korean passes were increasingly off the mark in the second half, and mistakes often happened deep in their own zone.

There were some adventures even on the last line of defense. In the 20th, goalkeeper Gu Sung-yun, making his first start of the tournament in place of ailing Kim Dong-jun, was stranded outside the box after charging well out in front for a loose ball, and was lucky that Faisal couldn't put one into the empty net.

Midway through the second half, Gu slipped and fell as he took his goal kick, almost setting up a one-on-one chance for Jordan.

With the top three nations here qualifying for the Olympics in Rio de Janeiro, South Korea will only need to win one more match to make their eighth consecutive Summer Games appearance. If they beat Qatar in the semifinals next Tuesday, they will finish no worse than second place. Even if they fall to Qatar, South Korea will get one final crack at an Olympic berth in the third-place match.

Qatar, with the backing of partisan crowds, have had the most productive offense so far at the tournament with nine goals in three group matches, followed by the 2-1 victory over North Korea in the quarterfinals.

South Korea head coach Shin Tae-yong said his players appeared flustered in the second half in the face of sudden Jordan attack.

Before they could regroup, the momentum had already shifted.

"At least we won the match without giving up a goal," Shin said. "I think we should be better in the next match."

Shin added that Qatar feature players with "great individual skills" but they're far from unbeatable.

"It's going to be a difficult match, because Qatar will be playing before home fans," Shin said. "We've already analyzed them, and I think we can beat them. It should be a big match." (Yonhap)