Widdop played his first match since dislocating his hip in June at the weekend in the secondary Queensland Cup.
With concerns over Widdop's match fitness, veteran Finch will get the nod at No.6 if he recovers from a damaged sternoclavicular joint, though coach Craig Bellamy won't make a final decision till later in the week.
Finch suffered the injury in the Storm's 23-22 final round win over Gold Coast on Saturday and, although very sore, he has been cleared of any fracture.
"Finchy has improved a lot in the last 48 hours and has had a cortisone injection," said Melbourne coach Craig Bellamy on Tuesday.
"We'll just see how he goes and see how Gaz (Widdop) goes.
"We probably won't make the decision until Thursday or Friday."
Souths named the side side that started against the Roosters last week and forward Jason Clark was listed on the bench despite being helped off the field at training on Tuesday.
Manly have recalled several players, including impact forward Anthony Watmough and star fullback Brett Stewart for Saturday's clash with minor premiers Sydney Roosters.
NSW Origin and Kangaroos star Watmough has missed the past few weeks after aggravating an existing knee complaint in the round 23 loss to South Sydney.
"A couple of weeks off has really freshened me up and I'm really hungry and ready to go," Watmough said.
Prop Brenton Lawrence also returns to the side, along with winger Jorge Taufua, who is back after serving a two-match ban.
The Roosters welcome back winger Roger Tuivasa-Sheck and backrower Mitchell Aubusson into their starting lineup and forward Luke O'Donnell onto an extended bench.
They will be forced into one change after listing Jared Waerea-Hargreaves to start, prior to him getting a one-game ban after being found guilty of a dangerous contact charge on Tuesday.
North Queensland co-captain and prop Matt Scott is set to make an earlier than expected return in Saturday's match against the Sharks after breaking his middle figure against that club in round 25.
The Queensland and Australia front rower has pushed Scott Bolton back to the bench, in the only change to the team that defeated Wests Tigers 50-22.
The Cowboys will be searching for a club record-equalling seventh straight win.
Skipper Paul Gallen, five eighth Todd Carney and backrowers Wade Graham, Jayson Bukuya and Anthony Tupou return for the Sharks.
The Canterbury Bulldogs have named fullback Ben Barba on the bench for a second straight week following his return from an ankle injury.
The Bulldogs and Newcastle have each named an unchanged starting lineup for their clash.
SOUTH SYDNEY RABBITOHS v MELBOURNE STORM at ANZ Stadium, 7.45pm
RABBITOHS: Greg Inglis, Nathan Merritt, Bryson Goodwin, Dylan Walker, Dylan Farrell, John Sutton, Adam Reynolds, Thomas Burgess, Issac Luke, Roy Asotasi, Chris McQueen, Ben Te'o, Sam Burgess. Interchange: Luke Keary, Jeff Lima, Jason Clark, George Burgess.
STORM: Billy Slater, Sisa Waqa, Will Chambers, Maurice Blair, Justin O'Neill, Brett Finch, Cooper Cronk, Jesse Bromwich, Cameron Smith, Bryan Norrie, Kevin Proctor, Ryan Hoffman, Ryan Hinchcliffe. Interchange: Jason Ryles, Tohu Harris, Jordan McLean, Kenneath Bromwich, Gareth Widdop (one to be omitted).
Referees: Shayne Hayne, Jared Maxwell.
CRONULLA SHARKS v NORTH QUEENSLAND COWBOYS at Allianz Stadium, 4.00pm
SHARKS: Michael Gordon, Sosaia Feki, Ben Pomeroy, Jonathan Wright, Beau Ryan, Todd Carney, Jeff Robson, Andrew Fifita, John Morris, Sam Tagataese, Luke Lewis, Wade Graham, Paul Gallen. Interchange: Isaac De Gois, Chris Heighington, Jayson Bukuya, Anthony Tupou, Bryce Gibbs, Ben Ross (two to be omitted).
COWBOYS: Matthew Bowen, Wayne Ulugia, Brent Tate, Kane Linnett, Antonio Winterstein, Johnathan Thurston (capt), Robert Lui, Matthew Scott (capt), Rory Kostjasyn, James Tamou, Gavin Cooper, Glenn Hall, Joel Riethmuller. Interchange: Jayden Hodges, Tariq Sims, Scott Bolton, Jason Taumalolo, Ashton Sims (one to be omitted).
Referees: Matt Cechin, Henry Perenara.
SYDNEY ROOSTERS v MANLY SEA EAGLES at Allianz Stadium, 7.00pm
ROOSTERS: Anthony Minichiello, Daniel Tupou, Michael Jennings, Shaun Kenny-Dowall, Roger Tuivasa-Sheck, James Maloney, Mitchell Pearce, Jared Waerea-Hargreaves, Jake Friend, Sam Moa, Mitchell Aubusson, Sonny Bill Williams, Frank-Paul Nuuausala. Interchange: Daniel Mortimer, Aidan Guerra, Isaac Liu, Dylan Napa, Luke O'Donnell, Martin Kennedy (two to be omitted).
SEA EAGLES: Brett Stewart, Jorge Taufua, Jamie Lyon, Steve Matai, David Williams, Kieran Foran, Daly Cherry-Evans, Brenton Lawrence, Matt Ballin, Brent Kite, Anthony Watmough, Justin Horo, Glenn Stewart. Interchange: Richie Fa'aoso, Tom Symonds, David Gower, George Rose, James Hasson (one to be omitted).
Referees: Ben Cummins, Gerard Sutton.
CANTERBURY BULLDOGS v NEWCASTLE KNIGHTS at ANZ Stadium, 4.00pm
BULLDOGS: Josh Morris, Mitch Brown, Tim Lafai, Krisnan Inu, Sam Perrett, Josh Reynolds, Trent Hodkinson, Aiden Tolman, Michael Ennis (capt), James Graham, Tony Williams, Josh Jackson, Dale Finucane. Interchange: Dean Halatau, Sam Kasiano, Tim Browne, Ben Barba.
KNIGHTS: Darius Boyd, James McManus, Joey Leilua, Dane Gagai, Akuila Uate, Jarrod Mullen, Tyrone Roberts, David Fa'alago, Danny Buderus, Willie Mason, Robbie Rochow, Beau Scott, Jeremy Smith. Interchange: Matt Hilder, Chris Houston, Neville Costigan, Alex McKinnon.
Referees: Ashley Klein, Gavin Badger.