The Australian, who missed three matches with a similar injury in March, is now facing an anxious wait to discover the extent of his latest setback and whether he can get back for the final against Wigan Warriors on August 24.
“I over-strode and it clicked,” McDonnell said. “I’ll do everything humanly possible to make myself in contention in four weeks.
“It depends on what grade it is – it can be a long one. We’ll check it out and go from there.
“I’m desperate to play. It’s bittersweet at the moment. To not play would be shattering, but it’s fingers crossed.”
McDonnell, a former player with Wests Tigers and Newcastle Knights, is in his first season at the KC Stadium after switching from city neighbours Hull KR and was a two-try hero of their cup quarter-final win over Catalan Dragons in Perpignan earlier this month.
His place yesterday was taken by the versatile Richard Whiting, who has appeared mostly in the back row of the pack this season but demonstrated his value to the side with an accomplished display as a makeshift full-back.
“He’s just one of those players who can slot into anywhere and do a job,” McDonnell said.
“It’s full credit to Rich – he was outstanding and really did the job well from the back.”
Whiting was beaten to the man-of-the-match award by Australian stand-off Daniel Holdsworth, whose tactical kicking proved decisive on his earlier-than-expected return from a three-match absence with a calf injury.
“He’s a quality player in the way he can control a game,” McDonnell added. “His calmness with his kicking game is something that is good for us. He was outstanding.”
Hull will be desperately hoping to have both Holdsworth and McDonnell fully fit to face favourites Wigan as they seek their first-ever win at Wembley.
They lost to St Helens on their last appearance there in 2008 while their last cup success in 2005 came at Cardiff’s Millennium Stadium during the period Wembley was being rebuilt.
“It’s a massive win,” said McDonnell, who went through agony during a nailbiting finish. “Warrington are a quality team and it was really tough the whole game.
“I’d rather be playing than watching. It’s terrible watching. I don’t know how the fans do it.
“It was tense in the last five minutes and, if we had lost, it would have been shattering. But the boys really dug deep. It’s outstanding to go to Wembley.”
Hull coach Peter Gentle admitted his side’s cup run has been a contributing factor behind their slide down the Super League table but he is hoping it can prove a catalyst for a reversal in form as they look to halt a five-match losing run against Widnes Vikings at the KC Stadium on Friday night.
McDonnell said: “We’ve got the team and we’ve got the game to win every game that we’re in – it’s just putting it together on the day.
“We’ve shown that we can perform against any team – it’s just consistency which is missing.”