Cardiff Blues coach Gareth Baber hailed Wales wing contender Alex Cuthbert as "sensational" following his two tries against Racing Metro.
But Baber also warned Wales to accept the once-capped 21-year-old will make mistakes if he plays in the Six Nations opener in Dublin on 5 February.
"If he's in their plans to play against Ireland, you've got to accept there will be errors in his game," he said.
"But he's sensational with ball in hand and he's a breath of fresh air here."
The Blues booked a European quarter-final with holders Leinster - another Dublin date Cuthbert can target in April.
But with Wales seeking a replacement for retired hero Shane Williams, Cuthbert will compete with fellow Blues players Leigh Halfpenny and Harry Robinson, as well as Scarlets pair George North and Liam Williams for a wing berth in the Six Nations.
Cuthbert capped his rapid rise to prominence by replacing rising star North late on in Wales' 18-24 defeat by Australia in December.
Baber added: "His [Cuthbert's] contribution was vital [against Racing Metro], as was Leigh's and in the short period of time that Alex has been playing at this level he's learned at every juncture.
"He's learned everything he can, a lot of the time from errors as well, and it always seems to me that's the best way to learn."