The former Australian Test scrum-half has been plagued with an unidentified virus for the past seven weeks and both he and his coach, Royce Simmons, have been waiting for the result of blood tests. At his best, Hasler has been an immensely influential figure. He has even invited comparisons with another Australian who wore the number seven shirt at The Boulevard - the incomparable Peter Sterling.
But there has been a price to pay in severe exhaustion for days following matches, and even after training sessions. Simmons would dearly love to have Hasler available this afternoon, but will not play him if he is, in the coach's phrase, 'too buggered to produce'.
Both Simmons and Hasler are in negotiation over extending contracts that end this season. Simmons may go home to run a Syndney restaurant in which he is a partner; Hasler, even at 33, has offers from Winfield Cup clubs.
After an inconsistent campaign, however, both men attach great importance to today's tie. If Hasler and other key players like Richard Gay, James Grant and Daniel Divet are fit, Hull are capable of giving the holders an uncomfortable afternoon.
'If we were playing them in the best out of 10, I wouldn't fancy our chances,' Simmons said. 'But in a single match, we've got a chance.' Although Hasler believes Wigan are as formidable as ever, it is still difficult to know what to expect from them at the moment: the collapse against Castleford? the scrappy effort against Wakefield? the vastly improved display at Widnes?
At their best, Wigan will move inexorably towards a seventh Challenge Cup in succession. One of their off-colour performances, however, will leave them vulnerable to catching a nasty and unfamiliar virus called defeat.
TODAY'S FIXTURES Silk Cut Challenge Cup Fifth round (3.0 unless stated) Doncaster v Oldham; Hull v Wigan (3.15); Hull KR v Featherstone (3.15); Keighley v Castleford (3.15); Whitehaven v St Helens (2.30); Widnes v Sheffield; Workington v Bradford Northern. Second Division Batley v London Crusaders (3.15); Carlisle v Dewsbury (2.0); Highfield v Swinton (3.0).Reuse content