Wales coach Warren Gatland admitted he brought on the wrong player during his side's 24-19 defeat to Fiji at the Principality Stadium on Sunday, their 10th successive loss.
Fly-half Sam Costelow played 47 minutes on the wing after Mason Grady was brought off with an ankle injury, but Gatland admitted a different player had been earkmarked to replace Grady.
"Probably the wrong player has gone on as a replacement. We talked about Ellis Bevan going on there," he said. "We had a long debate about the six-two split."
"I need to get to the bottom of that. We said we're going to put Ellis on. And then Sam ran on the field.
"I think he might have assumed he was the person going on. We had already had those discussions with Ellis that if we do lose a winger, you're going to need to cover us there."
Gatland appealed for both patience and time for his young side. However, he shrugged off suggestions his own position was under threat as Wales' run without success since last year's World Cup was extended in a surprise loss to the Pacific islanders.
"You can worry about that," he told reporters. "The pressure comes from the media as it's a narrative you create. That's OK."
"I believe that since the World Cup, with the players we've lost, we've invested in the youngsters and we've seen development.
"We need patience and time. I understand test match rugby is about winning. You control the narrative and write what you want."
Wales had looked promising and scored an early try to suggest they would end their winless streak but then made too many errors and let the game slip from their control.
"We tried to be positive and we showed glimpses of that. We could have been 20 points up but we were guilty of some things plus pretty unlucky on some calls against us. We're frustrated as we targeted this one to win," the veteran coach said.
"We need to fix up things defensively. Our kick chase could have been better. Those are fixes for us. The players are aware of that and they'll look at it," he added.
Wales' last victory was a 43-19 triumph over Georgia at last year's World Cup.
That was followed by elimination from the tournament by Argentina, then a Six Nations whitewash and mid-year losses to South Africa and twice to Australia.
Wales next meet Australia and then world champions South Africa in two more internationals this month.
Asked when the next Wales win might come, Gatland said: "Hopefully next week. It was supposed to be today. I've been around long enough to know test match rugby is all about winning.
"But it's about taking the pressure off the players so they can go out there and play. There's probably one or two moments there where players will think if they were more accurate, they could have created opportunities.
"At the moment the criticism directed at me is probably a little bit easier, it's not so much on the players, I'm reasonably comfortable with that.
"I've got broad enough shoulders to take that, but we will continue to work hard, keep our head down and we've got to come back and prove that for next week," the coach added.
Information from Reuters contributed to this report.
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