ROB McCusker admitted Wales were "naïve" in their defeat to Argentina which extended the back-rower's international losing curse.
The Scarlets captain replaced injured lock Alun Wyn Jones in the first half as the Pumas won 26-12, a fifth loss from five caps for McCusker.
It was a demoralising start to the autumn series for interim head coach Rob Howley and his side, and McCusker believes Wales only had themselves to blame.
"We were a bit naïve at times," he said.
"I still can't seem to get that win in the red shirt.
"Argentina are looking better year on year and, unfortunately, we were their latest victims.
"We knew what sort of challenge we would get from them but we did not deal with them."
With Wales opting not to select specialist lock cover on the bench, McCusker came on at blindside flanker and regional team-mate Josh Turnbull moved to the second row to cover for Jones.
McCusker said Wales were considering resting some of their first-choice players for Friday night's match against Samoa, but Saturday's result would seem to extinguish such an idea.
With matches against world champions New Zealand and Australia to come, Wales could be staring at a series whitewash so victory against Samoa is imperative.
"We wanted to get the series off to a good start with a win, so it's disappointing," said McCusker.
"We need to get back on the training field and put things right on Friday.
"Samoa have a lot of quality and physicality, even if they do not all have the experience at the top level.
"We might have wanted to rest a few players after the Argentina match but I don't think we can do that now.
"Samoa will be gunning for us after seeing us lose this game."