The full-back sustained the knock during the first half of Friday evening's 42-14 Super League win over Salford - a game he only started after passing tests following a blow to the head against Castleford last weekend. Coach Brian McDermott confirmed he does not expect Hardaker to make next week's fixture and also ruled Ryan Bailey out of the game.
He does expect veteran forward Jamie Peacock and the versatile Brett Delaney to return, though, and also gave Joe Vickery a fighting chance of playing ahead of schedule, but the news about Hardaker did gave McDermott a headache. "He had a bang to the thumb. He needs an x-ray and that's not looking good," he said.
"He will have his x-ray over the weekend but he can't use his thumb at the moment. I'm a realist and at this stage it's not looking good. We have a few options at full-back. We will have a look at some stuff, but Kallum Watkins is a likely option at this stage."
Despite Leeds running in seven tries - two of which went to former Red Joel Moon - it was hardly a vintage show from the Rhinos, who came up against a Salford side who had both form and history against them. They have now won just one of their 33 Super League games in total and have lost 10 matches in a row against all opponents.
Their rebuilding process continues under new ownership and with a thrown-together squad, and Leeds could have faced stiffer opponents as a warm-up, but McDermott still had plenty to ponder.
"It was scrappy. We didn't get to grips with the game and it was not a great spectacle," he said. "There were times when we had lots of options and things to go at, but we overplayed. It prepared us for next week because some lads got good game time, and those are the positives.
"We will take the positives and, if we had have had a shocker, we would have waved it off. We wanted to take care of what we could and we did that, to a degree."
Salford offered little more than a mid-game flurry and their aggregate score for the season is 124-16. Coach Phil Veivers said: "I saw an improvement from the last two games and was happy with that.
"They had a dig and put the effort it. It was there from the first minute to the 80th minute, but there was a little bit less smartness about us at times. We gave them three tries by dropping the ball, but they're a good side who are all playing for positions and we won't take anything from them. They scored 42 points."