Japan back-row forward Amanaki Lelei Mafi admits that the absence of injured Rugby World Cup stars including Ayumu Goromaru and Michael Leitch hurt the Brave Blossoms in their two test-match defeats to Scotland.

But the Tonga-born man mountain has backed their youthful replacements to fight for a place in the 2019 World Cup team on home soil after a narrow 21-16 loss to the Scots in front of 34,073 at Ajinomoto Stadium on Saturday night.

"We missed them," Mafi said of his absent teammates, who also included scrum half Fumiaki Tanaka and winger Akihito Yamada. "We have a lot of new members. It has been difficult but I think with the new boys coming up it has been a really good experience for them to work hard for their own positions.

"I'm very proud to be part of the Japan team. We just came one week before the start of the tournament so it has been hard, but I'm still proud."

Japan looked set to avenge its 26-13 defeat to the Scots at Toyota Stadium the previous week when scrum half Kaito Shigeno scored an earth-scorching try midway through the first half on Saturday to put the Brave Blossoms in control.

But Scotland gradually chipped away at the lead with a series of penalty kicks from scrum half Henry Pyrgos and replacement Greig Laidlaw, eventually overtaking the home side with 10 minutes remaining before closing out the win.

"As with the last game, giving away penalties is the thing we have to work on, at the breakdown and so on," said the 25-year-old Shigeno, who filled in for two-time World Cup veteran Tanaka.

"It's up to the players to play in a way that suits the referee."

Leitch and Goromaru, who earlier this month joined French giants Toulon, took part in a pre-game ceremony before watching the match from the stands. But replacement fullback Rikiya Matsuda insisted that the presence of superstar Goromaru added no extra pressure to his performance.

"Wearing the No. 15 shirt for Japan is a huge source of pride and I feel that responsibility," said Teikyo University student Matsuda. "I took Goromaru's place in the team but I didn't play well and now I have to reflect on why that was and how much I can use it to get better.

"I was concentrating only on my own performance. I didn't feel any nerves just because of Goromaru."

The Scots' victory preserved their perfect test-match record over Japan, including a 45-10 win at last year's Rugby World Cup that marked the Brave Blossoms' only defeat of that tournament.

Ajinomoto Stadium will host the opening game of the 2019 World Cup, and Scotland fullback Stuart Hogg was impressed by the venue and the opposition.

"I thought Japan were outstanding," he said. "They came flying out the blocks early doors and chucked everything at us. Obviously we're very happy to come away with the win. We know we have to improve but credit to Japan, it was a really good test match.

"We've played at two cracking venues and the crowd has been phenomenal so we're very much looking forward to being here. We're very excited to have the World Cup here."

Japan interim head coach Mark Hammett will not make it as far as the 2019 World Cup, however, having completed his three-match brief including a 26-22 win over Canada in Vancouver on June 11.

"I feel perhaps the last two tests we've just been slightly disrespected as a team and what we can achieve," said Hammett, the regular head coach of Japan's Super Rugby side, the Sunwolves.

"I felt that in the second half we didn't get the reward. There's obviously a reason why the ball was being slowed down. We worked really hard for that but probably didn't get the outcome that we believe we should have had.

"Having now been in Japan for six months and understanding how hard these guys work and how smart they are tactically, I'm not sure that the rest of the world understands where this group is getting to."