Captain Dewi Lake says Wales let themselves down during the lacklustre 28-21 Nations Championship victory against Japan in Cardiff.
Josh Adams added two tries to scores from prop Archie Griffin and wing Louis Rees-Zammit as Wales claimed a bonus-point win.
This was their second victory from four games in the competition but Lake was left frustrated with aspects of the performance.
"There were massive parts of that game where we let ourselves down," he said.
"Getting into camp, we said we were going to do things that we probably didn't do against Japan."
"That's disappointing but this is a group that wants to grow and will challenge each other."
In front of a crowd of 52,425 supporters, Wales had to hold on for only the fourth win in Steve Tandy's 13 Tests in charge, two of which have come against Japan.
Lake said a victory should not be underestimated with Wales having suffered recent losing streaks, which included a record 18 consecutive Test defeats in a row.
"A win is massive for this group, for the confidence and trust we'll get in each other," he said.
"We were happy with the win and it's something we've not done often enough, so I am proud of the boys."
Wales remain fifth in the northern hemisphere table but face much tougher challenges this month.
New Zealand, fresh from defeating Scotland, are the visitors to Cardiff next Saturday before Australia play at the Principality Stadium on 21 November.
"If you look at the two Test matches, we did things today that weren't good enough to compete in those games," said Lake.
"We'll have to get a lot right next week and fix some stuff."
Head coach Tandy said he was expecting more from his side this weekend.
"It's good to start the campaign with a bonus-point win but I can't run away from the performance when I talk about it," said Tandy.
"There are elements of the performance we definitely need to improve. I thought we'd be better than that in some elements."
"There was good stuff from us, in terms of the line breaks and how we opened Japan up, but we weren't ruthless enough."
"We'll definitely have to do that for the next couple of games but it helps to review after a win."
Japan head coach Eddie Jones said it was an opportunity missed to win a first game in Cardiff against Wales.
"That could have been a historic win for us but you've got to be good enough to take advantage of those mistakes," he said.
"We weren't quite good enough and it was certainly a missed opportunity."
Jones said he was proud of his young team but believes they needed to be more clinical.
"If you watch rugby now, once you get in the 22 and if you don't take points from that, that's the difference in the game," said Jones.
"We had three opportunities but we didn't take chances and Wales did. Their points-per-entry was higher than ours."
Jones questioned some aspects of the interpretation of New Zealand referee Paul Williams at the contact area.
"I hope I'm not going to get in trouble for this but there was one penalty for not supporting your weight at the breakdown and it was against us," said Jones.
"Anyone watching that game, can you think there was just one ruck where the supporting player was off his feet?"
"That can be the difference between winning and losing."
"I'm not complaining, I'm just saying sometimes you don't get the rub of the green."
"That can happen. You've got to suck it up and get on with it. Actually maybe I am complaining!"
Japan travel to face Jones' former England side at Allianz Stadium at Twickenham next Saturday.
