The Tigers are in excellent form, scoring more tries than any other team for the second season in a row, and losing just two matches since January.
This will be their eighth consecutive appearance in the final, and they will need big performances across the pitch to beat Harlequins.
Teenage fly half George Ford is expected to start, while the England international Toby Flood will begin on the bench.
Quins' are expected to recall Ugo Monye and Danny Care to the squad, as they both recover from injury.
The west Londoners have won their last four finals that they have featured in, including last season's dramatic Challenge Cup victory over Stade Francais.
Tigers fans will point to their April match against Harlequins, in which the Midlands side came out on top.