Wales captain Tommy Reffell admits his team can afford no slip-ups when they face Japan at the World Rugby U20 Championship on Thursday.

The Leicester Tigers back rower knows that a shock defeat would halt his team’s chances of progress from Pool A following their heavy 42-10 to New Zealand at the weekend.

The Baby Blacks had three players sent to the sin bin, but never appeared unduly troubled and Reffell concedes that Welsh standards slipped from their superb opening victory over Australia.

Reffell said: “The defensive errors really cost us. Everyone knows that against a team like New Zealand you can’t make errors like that because they’ll capitalise on them and punish you.

“Luckily we play a sport where you get a second chance to redeem yourself and all eyes will be on the Japan game now. It is a must-win match.”

It was a second bonus-point win of the campaign for the defending champions at Stade de la Mediterranee in Béziers.

Vilimoni Koroi and Tom Florence both took a 10-minute breathers as New Zealand led 25-10 at the break before Tanielu Tele’a saw yellow at the end of the second half.

Despite their ill-discipline, New Zealand never looked like falling victim to an upset with scrum-half Xavier Roe expertly controlling play and keeping Wales pinned back in their own 22 for long periods.

New Zealand captain Tom Christie said: “What a game of rugby. We knew we were in for a battle.

“I’m really pleased with how my boys came up over that. The good thing about New Zealand rugby is the amazing depth, number one to 15 know we have people biting at our heels so we are really motivated to keep going and put those performances in.”

Roe deservedly got his name on the scoresheet from a quickly-taken tap penalty, shortly after Wales had lost Lewis Ellis-Jones to the bin, with the rest of New Zealand’s tries coming from Billy Proctor, Bailyn Sullivan, captain Tom Christie and replacement tight-head Tevita Mafileo.

Sullivan created the first for Proctor in the third minute with a powerful run involving two hand-offs and an offload before No.8 Taine Basham got Wales back on level terms with a brilliant finish in the corner after Koroi had been sent to the sin-bin for sticking out a hand to stop a Welsh two-on-one.

Questionable decision-making and some needless penalties cost Wales the chance to press home their advantage and, after an exchange of penalties between Plummer and Cai Evans, Sullivan touched down after a neat offload from Tele’a.

Koroi’s show-and-go and another offload from Sullivan set up Tom Christie for his second of the tournament with 29 minutes gone. Plummer added the extras and then booted a 48-metre penalty on the stroke of half-time as the rain started to pour down. By this stage, Florence’s involvement had been temporarily curtailed due to a dangerous tackle.

Determined defensive sets from Wales meant that for all their dominance New Zealand only had a second Plummer penalty to show for their efforts – until the 64th minute when Mafileo charged down Ben Thomas’ attempted clearance and then scooped up the loose ball from the greasy surface to race home from 15 metres.

New Zealand remained camped in Welsh territory and after several near-misses Roe darted over from close range.

The game ended on a low note for New Zealand though when Tele’a became the third player to be sent to the sin-bin for a late tackle.