JAPAN captain Maya Yoshida (pictured, AFP) admitted that the Blue Samurai need to show more ruthlessness after they edged Oman 1-0 to reach the Asian Cup knockout phase on Sunday.

A controversial Genki Haraguchi penalty sent the four-time champions into the last 16 after a lacklustre performance that left Yoshida complaining about the team’s dismal finishing in Abu Dhabi.

“We have to be more clinical,” Yoshida said after Japan’s second successive win in Group F.

“We should have scored two or three more – that’s why we struggled in the last 10 minutes. It’s always difficult when you’re 1-0 up and the defence are up against it.”

Yoshida also felt that fortune had favoured Japan, who were awarded a penalty when Haraguchi tumbled theatrically under minimal contact, and got away with one when Yuto Nagatomo appeared to use his hand to block a shot just before half-time.

“It was tougher than we thought it would be,” said the Southampton defender.

“We were a little bit lucky with the penalty we had – and the one not given as well. But the most important point for us was to get through the group.

“It’s important for us to build confidence,” added Yoshida, one of Japan’s surviving old guard after coach Hajime Moriyasu dropped the likes of Shinji Kagawa and Shinji Okazaki in favour of a new-look squad at the Asian Cup.

Japan, who reached the knockout stage at last year’s World Cup, also failed to impress in beating Turkmenistan 3-2 in their Asian Cup opener.

Yoshida has called on a marked improvement from the side if they are to challenge joint favourites Iran and South Korea for the title.

“Our performances are still not good enough clearly,” said the 30-year-old. “But I still have confidence we will get back on track.”

Japan will take on either Saudi Arabia or Qatar in the last 16 – the 2022 World Cup hosts firing a warning by crushing North Korea 6-0 earlier on Sunday.

Iran though have looked the team of the tournament so far, while South Korea, beaten in the 2015 final by hosts Australia, will be boosted by the arrival of mercurial Tottenham forward Son Heung-min.

“I saw Iran at the World Cup, where they played really, really well,” said Yoshida, acutely aware of the dangers posed by the Asian Cup’s top sides.

“I was really surprised, impressed. And of course Australia, South Korea – they’re always the most difficult opponents.