Saracens lost their first European game of the season 25-10 at Clermont Auvergne last weekend whereas Leinster downed big-spending French outfit Racing Metro 38-22.
And director of rugby Brendan Venter has warned Sarries they must find their killer touch if they're to avoid racking up back-to-back defeats.
"If we don't finish our chances against Leinster, we won't beat them," said Venter. "They are too classy an outfit.
"We created a lot against Clermont, so many try-scoring opportunities, but with a lot of them it was us that actually made the error.
"We need to finish, we need to take our points. Give Leinster a half-chance, and they score."