Up to four Wigan Warriors players added to the injury-list

Liam Marshall is facing a short spell on the sidelines with a shoulder injury.

And Joe Greenwood (knee), Thomas Leuluai (shoulder) and Sam Powell (head) are all doubtful for Saturday's headlining game against Warrington at Anfield.

Of those three, Greenwood appears to have the best chance of playing after checks cleared him of any major damage to his knee.

He was replaced during the first-half of last Saturday's 33-16 loss to Catalans at Camp Nou.

"Joe hyper-extended his knee, but we'll give him until Friday and if he has full range by then he'll be in," said Lam.

"Sam Powell needs to pass a head test, and Tommy is a doubt as well - he's probably 50/50 at the moment but we'll see how he is on Friday."

He will be hoping at least one of Powell or Leuluai will play, as the loss of both would leave him short of options in the crucial halfback and hooker roles.

Jake Shorrocks is fit to return, possibly to partner George Williams in the halves, but there is no other obvious candidate for the No.9 spot.

Jarrod Sammut and Liam Farrell are nearing returns from injuries - they travelled with the squad to Barcelona - but are both thought to be another two weeks away.

Young hooker Amir Bourouh, who made his senior debut at Salford on Easter Monday, is out with illness while several other Under-19s players are suspended.

Marshall, meanwhile, may be out for a month with his injury, though an exact timeframe has yet to be determined. He is the third front-line winger to be ruled out, alongside Dom Manfredi and Tom Davies who are both out for the season.

With Joe Burgess on the left-wing, Lam's options on the right are French livewire Morgan Escare, centre Chris Hankinson or fringe player Craig Mullen.

Given both Escare and Hankinson have utility value, the Warriors boss says he will wait to see how the other players are on Friday before deciding the composition of the side.

Warrington have injury concerns of their own after full-back Stefan Ratchford was ruled out for 16 weeks with a torn pectoral.

The winners of Saturday's match will receive the Locker Cup - a pre-season trophy which was shelved when Super League was launched in 1996.