Tigers vice-captain Allen and Tonga international forward Mafi are both selected among the replacements.
Director of rugby Richard Cockerill makes two changes in the forward pack as Neil Briggs starts at hooker, and Ed Slater is replaced by Sebastian de Chaves after taking a knock in the match against Bath last Sunday.
De Chaves lines up alongside Louis Deacon who makes his 66th European appearance for the club, moving ahead of Ben Kay and into third place in the Tigers' all-time list behind former captains Geordan Murphy and Martin Corry.
Argentina international prop Marcos Ayerza makes his 150th starting appearance for the club since his debut in 2006.
Kick off at the Stadio Monigo in Treviso is at 2.35pm local time, 1.35pm UK time. There is live TV coverage on the red button on Sky Sports 2. Or keep up to date with Tigers on the club's official Facebook and Twitter feeds.
Leicester Tigers (v Benetton Treviso, away, Saturday)
15 Mathew Tait
14 Niall Morris
13 Vereniki Goneva
12 Toby Flood (c)
11 Miles Benjamin
10 Owen Williams
9 Ben Youngs
1 Marcos Ayerza
2 Neil Briggs
3 Dan Cole
4 Louis Deacon
5 Sebastian De Chaves
6 Jamie Gibson
7 Julian Salvi
8 Thomas Waldrom
Replacements
16 Rob Hawkins
17 Boris Stankovich
18 Fraser Balmain
19 Steve Mafi
20 Jordan Crane
21 David Mélé
22 Anthony Allen
23 Matt Smith
Benetton Treviso: 15 Brendan Williams, 14 Angelo Esposito, 13 Michele Campagnaro, 12 Andrea Pratichetti, 11 Luke McLean, 10 Mat Berquist, 9 Edoardo Gori, 1 Michele Rizzo, 2 Leonardo Ghiraldini, 3 Lorenzo Cittadini, 4 Antonio Pavanello (c), 5 Valerio Bernabo, 6 Christian Loamanu, 7 Paul Derbyshire, 8 Robert Barbieri
Replacements: 16 Franco Sbaraglini, 17 Alberto de Marchi, 18 Ignacio Fernandez Rouyet, 19 Marco Fuser, 20 Marco Filippucci, 21 Francesco Minto, 22 Fabio Semenzato, 23 James Ambrosini