Francesco Minto thought he had mauled his way over the line only to see the TMO rule out the score and the Irish province eventually went on to triumph 27-3.
Treviso's last GUINNESS PRO12 win came against Cardiff Blues back in February but Casellato has urged his troops to keep their heads up as they attempt to end their unwanted streak away to Connacht this Friday.
"I wanted to make it clear to the players that they must not give up," said Casellato. "Leinster came here with all their players back but in the first half we produced good things in defence and in attack, even if they almost immediately scored a try.
"They certainly know how to play and their second try came in the last minute before half-time with a 50-50 on high ball.
"Certainly in the second half the team struggled though. I saw us miss easy one-on-one tackles and they are good at moving the ball which put us in difficulty.
"It is not our system of attack that does not work - two or three times there was an overlap but we just did not capitalise."
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