Forsyth scored two tries in the opening win over Tucuman before starting on the bench in the victory over Buenos Aires.
Coach John Fletcher again makes a raft of changes as players are given their opportunity to stake a claim for a place in the international against Argentina on August 3. England will now also play another warm-up game in preparation for that match, against Uruguay on July 30.
Fletcher said: We are really looking forward to the game. If it is anything like the two matches we have played so far then we are expecting another very physical game. We have had some good training sessions this week and England senior coach Mike Ford delivered a very useful session on defence on Friday which the lads enjoyed. Hopefully, theyll be able to put that into practice against Mendoza.
Tigers duo Sam Harrison and Joe Cobden are included among the England replacements for Sundays match.
1 Joe Marler (Harlequins), 2 Jamie George (Saracens & Haileybury), 3 James Currie (Bath Rugby & Millfield), 4 Tom Holmes (Sale Sharks & Sandbach), 5 James Gaskell (Sale Sharks & Sandbach), 6 Sam Jones (London Wasps & Aylesbury Grammar), 7 Jacob Rowan (Leeds Carnegie & Bradford Grammar), 8 Alex Gray (Newcastle Falcons & Barnard Castle, captain); 9 Jordi Pasqualin (Gloucester Rugby & The Kings School), 10 George Ford (Leeds Carnegie & Rishworth), 11 Sam Edgerley (London Irish & Wellington College), 12 Owen Farrell (Saracens & St Georges), 13 Andy Forsyth (Leicester Tigers & QEGS Wakefield), 14 Marcus Watson (London Irish & St Georges College), 15 Tom Catterick (Newcastle Falcons & Barnard Castle)
Replacements: 16 David Blackwell (Gloucester Rugby & Hartpury), 17 Mako Vunipola (Bristol Rugby & Millfield), 18 Jamie Gibson (London Irish & Marlborough College), 19 Joe Barker (Leeds Carnegie & QEGS Wakefield), 20 Sam Harrison (Leicester Tigers & John Cleveland College), 21 Rory Clegg (Newcastle Falcons & Barnard Castle), 22 Christian Wade (London Wasps & RGS High Wycombe), 23 Joe Cobden (Leicester Tigers & King Edward VI Lichfield), 24 Jack Wallace (London Wasps & RGS High Wycombe)