Bradford & Bingley prop Ronnie Kelly is suffering from a partially collapsed lung.
The former Otley player, who has made a comeback recently after retiring at the end of last season, was only diagnosed with the problem this week.
Kelly watched last Saturday's 38-10 home victory over Darlington Mowden Park from the sidelines.
It is hoped that he will return for the potentially vital clash when the second-placed Bees visit current National League Three North leaders Nuneaton on Saturday, February 25.
Bees' head coach Geoff Wappett says: "Ronnie doesn't need to take anything or have an operation. He just needs quality rest time."
Bradford & Bingley are hopeful, however, that left winger Mark Kirkby will return tomorrow at Fylde after pulling out on the morning of the match last weekend with tendinitis in a leg.
If he fails a fitness test, Tim Bennett will continue on the flank. Barry Clark comes into the second row, replacing Richard Hughes, who is on the bench after receiving seven stitches in a head wound against Mowden Park.
Tongan flanker Latu Makaafi will keep Hughes company on the bench if he recovers from a shoulder injury.
Wappett said: "Fylde are a tough proposition at home and they have a very big pack.
"It is up to us to secure enough ball and then move it wide where we have more pace."
Cleckheaton travel to Mowden Park on the back of what former British Lion John Bentley described as "our best performance of the season". Cleckheaton lost 21-19 at home to Blaydon and, considering the resources of both sides, Alan Bentley reckoned his namesake's opinion was spot on.
He said: "Blaydon were at full strength, Martin Shaw apart, and had only just lost to Bradford & Bingley the week before."
Cleckheaton's only changes this week are prop rotations, with Carl Mason and Jim Lamptey starting in place of Steve Johnson and Paul Turner.
A registration technicality prevents Yorkshire Under-20s squad member Oliver Pursglove from making his Wharfedale debut on the wing at Halifax in National League Two in place of the injured James Hutchinson.
The reshuffle puts Chris Malherbe on the wing, Andy Baggett partnering Mark Bedworth in the centre and Chris Meehan returning at fly half.
Martin Halsall makes his first start for the club at prop, and the evergreen Jonathan Davies takes a bench place.
Bradford Salem have centre Steve McManus on the bench after hamstring trouble at Pontefract in Yorkshire Division One, while Keighley have Johnny Harrison and Adam Balderstone at half-back at leaders Sheffield Tigers.
They replace Liam McGee and James Tillotson. Michael Feather resumes in the second row while Leigh Sugden returns to the back row.
Meanwhile, presistent injuries, business and family commitments have caused Keighley prop Mark Smith to annouce his retirement from rugby.
Baildon, who have signed second row Richard Smith from Old Otliensians, have a Yorkshire Three derby at Skipton, while Wibsey recall veteran Andy Todd at centre for their Yorkshire Five North West derby at Burley - Wibsey's first game in six weeks.
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