Lappin, who has struggled with a thigh injury since round 1, has been selected in the centre and is a likely starter. Drummond made his return with the Suncoast Lions last month and has been gaining valuable match fitness ever since.
Schmidt has been rewarded for a series of strong performances in the reserves with selection in the senior squad.
The 25-man squad will be cut to 22 on Friday.
The full squad for this week is;
B: Chris Johnson (2), Daniel Merrett (21), Jason Roe (29)HB: Jed Adcock (7), Jared Brennan (17), Robert Copeland (30)C: Justin Sherman (11), Nigel Lappin (44), Cheynee Stiller (32)HF: Scott Harding (5), Jonathan Brown (16), Tim Notting (8)F: Michael Rischitelli (35), Joel Patfull (24), Ashley McGrath (9)R: Jamie Charman (19), Simon Black (20), Luke Power (6)Int: From - Richard Hadley (14), Colm Begley (46), Beau McDonald (43), Marcus Allan (42), Ben Fixter (4), Chris Schmidt (13), Josh Drummond (39)
