Morton have lost Kyle Wilkie from the squad that heads north to face Highland League Turriff United.
The midfielder picked up a leg knock in a midweek reserve game.
Wilkie is joined on the sidelines by Peter MacDonald, Archie Campbell and Tony Wallace, however, Cappielow manager Allan Moore knows that his side are still hot favourites to go through.
Moore said: ``Whatever side we put out should be strong enough to see off Turriff but we may have to show patience to do it.
``They have done well to reach this stage in their first ever season in the competition, and will want to keep their run going, but we have to go out and do our business professionally as this is a no-win tie for us.''
Midfielders Darren McAllister and Ritchie Ligertwood are suspended for Turriff's first-ever meeting with a SFL side.
The Aberdeenshire team will also be missing skipper Dave McKenzie after he suffered knee ligament damage recently and new loan signing Mike McKenzie is ineligible as he is cup-tied.
Co-managers James Duthie and Mark Simpson have other concerns as well with Gary Harris, Nick Gray, Robbie Allan and Grant Pennett all injury doubts.
Simpson said: ``We have enjoyed a fantastic run in our first ever Scottish Cup campaign and being at home gives us more of a chance against Morton however we are huge underdogs. They are a strong experienced side but we will give it our best shot.``