Harry Kewell warned there was "still a long way to go" after his Yokohama F-Marinos claimed a narrow Asian Champions League final advantage over Hernan Crespo's Al Ain with a 2-1 win in Saturday's first leg in Japan.

Mohammed Abbas scored in the 12th minute for United Arab Emirates side Al Ain but Yokohama's Asahi Uenaka levelled midway through the second half before substitute Kota Watanabe grabbed the winner six minutes from time.

Kewell and Crespo were meeting as coaches almost 20 years after facing each other as players in the UEFA Champions League final in Istanbul.

Crespo was part of the AC Milan side that took a 3-0 half-time lead before Kewell's Liverpool famously came back to draw 3-3 and then win on penalties in 2005.

Kewell knows that anything can happen in football and he warned his players to stay switched on for the second leg in the UAE in a fortnight's time.

"I know in this game that it can be taken away from you so quickly," said the Australian, who has led Yokohama to their first Champions League final only four months after taking over.

"We have to understand that there is another 90 minutes to play and it's going to be very difficult.

"They can enjoy the moment but there's still a long way to go in this tie."

Al Ain are the UAE's most successful club and they are playing in the final for the fourth time, having won it in 2002 and reached the decider in 2005 and 2016.

Argentine great Crespo said he was "very confident" that his team can overturn the deficit in the second leg.

"We know what it means to play at home with our fans -- today was not easy because their fans shouted and supported their team," he said.

"In two weeks it will be the opposite. We need to take advantage of that.

"We believe we can do it."

- Late turnaround -

Yokohama made a bright start in front of almost 55,000 home fans and Elber and Yan Matheus both had attempts at goal within the first five minutes.

But Al Ain threw a spanner in the works with the opening goal just over five minutes later when Abbas stuffed home the rebound after goalkeeper William Popp had denied Soufiane Rahimi.

The UAE side thought they had scored a second in the 30th minute when Matias Palacios fired the ball between Popp's legs, only for a VAR check to rule it out for offside.

Yokohama had several chances to get back on level terms but found Al Ain goalkeeper Khalid Eisa in inspired form.

"I'll always say scoring goals is the hardest thing to do in football," said Kewell.

"People can criticise but to be in that moment is difficult."

Yokohama were much scrappier in the second half, but they got their equaliser when Matheus's cross picked out Uenaka to head home in the 72nd minute.

Watanabe then completed the turnaround in the 84th minute with a goal that was awarded after a VAR check, having been initially given as offside.

"I'm not going to sit here and say the game's finished -- I'm not silly enough to do that," said Kewell.

"Their team is confident enough to get a goal but we're also confident to go out there and score goals."