Stephen Jones has urged his Scarlets team mates to "throw everything at Leinster" when they meet the Heineken Cup champions again in Dublin this weekend.
The Irishmen picked up an impressive five points as they ran in four tries in their 32-7 triumph in Pool 6 at Parc y Scarlets and were at their peak in the first-half in which they scored 22 unanswered points.
The Scarlets had won their two opening matches, but now face an uphill task to qualify with both the champions and London Irish ahead of them on 10 points.
"We have to give credit to Leinster, they were outstanding. Tactically and technically they were very good and they won all the crucial battles in the air and on the floor," admitted Wales and British & Irish Lions outside half Jones.
"We played with a bit of momentum in the second half, but we made far too many silly mistakes and weren't clinical enough. It was very difficult in the first-half because we had limited possession.
"We need to be more efficient and I guess it is back to the drawing board for us this week. We have got a young squad and we have to respond in Dublin.
"The return game will be a good test of our character and we will learn who really wants to play for the jersey. Rugby is a game played in the head and we have to make sure we are mentally tough enough next week.
"There is still everything to play for in the Pool and we have to go to the RDS and throw everything at them."