Winger Kyle Steyn said Scotland supporters have every right to question whether the team have the mettle to get the job done against tough opponents in the wake of their narrow defeat by New Zealand and the collapse against Argentina this month.
The Scots fought back to level with the All Blacks at Murrayfield on November 8 before letting the game slip away in the last eight minutes. On Sunday, Scotland led the Pumas 21-0 but allowed the visitors to score five unanswered tries and lost 33-24.
"It's just not good enough,” Glasgow Warriors captain Steyn told reporters ahead of Sunday's test against Tonga.
“I'm sure the people of Scotland are sick of hearing excuses. To be honest, we don't have any.
"We're not hiding from this. It's just at some point we're going to have to ask ourselves the question: ‘Do we have the marbles in the big moments?’
"Until we show it, then fair enough to the Scottish people for doubting that. But, yeah, we'll try to make sure we find the answers.”
Steyn lamented Scotland's inability to do the basics in the tough moments.
“We've had chances where we certainly could have put our mark on the game and probably taken the win, and both times we've let New Zealand and we've let Argentina back in and let them take the win," he added.
Scotland left the field to jeers from some fans after the loss to Argentina but Steyn said many in the crowd appreciated that the players had given their all.
“We're really thankful for the fans that stayed behind and clapped us because, again, there's no shortage of effort there. We thank the people that can appreciate that," he added.
"And to those that booed, I think we just appreciate that the people of Scotland demand a higher standard of us, and we demand that of ourselves too.
"I'm sure they're doing that because of the way they're feeling, and that's a reflection of the way we played, so fair enough."