Jeonbuk Hyundai Motors have dug themselves into a huge hole in the AFC Champions League after dropping the opening leg at home against their Japanese rival.

Kashiwa Reysol of Japan's J. League blanked Jeonbuk of the K League Classic 2-0 in the first leg of their round of 16 series on Wednesday night. At Jeonju World Cup Stadium, about 240 kilometers south of Seoul, Masato Kudo and Tatsuya Masushima each scored for the visiting club.

Jeonbuk was the champion in 2006 and the runner-up in 2011 at the premier club football tournament in Asia. Down two goals after one leg, Jeonbuk must win the away match next Wednesday in Kashiwa to advance.

Kashiwa will try to secure its first AFC quarterfinals berth.

The aggregate score after two matches will determine who will reach the quarterfinals. The "away goals" rule is in effect, meaning if the two teams are tied in the aggregate score after two matches, then the team that has scored more away goals will be declared the winner.

If teams end up with the same number of total and away goals, then two periods of extra time and, if necessary, a penalty shootout, will determine the winner.

Kashiwa has beaten Jeonbuk in three straight games in AFC play.

During the group stage last year, Kashiwa defeated Jeonbuk twice, by the scores of 5-1 and 2-0. The second victory eliminated Jeonbuk from the group phase.

On Wednesday, Kudo headed in the first goal only two minutes into the match, while Masushima's insurance came midway through the second half. Following the loss, Fabio Lefundes, Jeonbuk's interim head coach, said his team couldn't recover after the first score.

"We conceded an early goal and that made the rest of the game very hard," the Brazilian said. "We still had a lot of chances, but we were unable to capitalize (on them)."

Lefundes said the away game next week will be "a challenge," which will be rendered even more difficult for the banged-up Jeonbuk team.

On Wednesday, the team missed three regulars to injuries.

Defender Jung In-hwan was out with an ankle injury. Midfielder Kim Jung-woo had missed his previous two games with right calf pains and couldn't recover in time for Wednesday.

Finally, Jeong Hyuk, another midfielder, suffered a compound fracture in his right wrist earlier this month and has been ruled out for up to six weeks.

Lefundes seemed resigned to the fact that he will be without some of his usual starters, and said he will use essentially the same lineup next week that he did on Wednesday.

"Our injured players will not be back for the second leg," he said. "Injuries are piling up on our team. At this point, I think I fielded the best squad that I could (on Wednesday)."

Aside from Jeonbuk, FC Seoul is the other K League Classic club still in action in the AFC. On Tuesday, FC Seoul played Beijing Guoan of China to a 0-0 draw and must win at home next Tuesday to reach the quarters.

The K League Classic is home to three of the past four AFC champions. (Yonhap News)