Leeds are hoping centre Kallum Watkins can recover from a wrist injury in time to play in Friday's World Club Challenge against Manly at Headingley.
But Rhinos coach Brian McDermott rates former England winger Lee Smith's prospects as "slim" after damaging his ribs in Saturday's defeat at Wigan.
"If he's popped a rib cartilage or torn some of those muscles around that area, it's pretty serious," said McDermott.
"I don't want to write him off. But he sore and not looking great," he added.
"We'll give him until the 11th hour. Given that he's started off this year pretty well for us and his head is in the right place, I'll give him as long as we can."
The Rhinos have an obvious replacement in Ben Jones-Bishop, a member of their Grand Final-winning team in October, who was also in the England squad for the Four Nations Series.
"We've got a couple of options there," McDermott added. "Ben Jones-Bishop is probably the notable one.
"If it's him, I'm sure he'll be doing everything possible to keep hold of his shirt."
The Australian champions' arrival last weekend coincided with a rise in temperatures that removes any lingering doubt over Friday's game and will be a relief to the Rugby Football League after ignoring the claims of Elland Road's undersoil heating.
Leeds are expecting a 20,000 full house as they look to become the first English winners of this fixture since they themselves beat Melbourne 11-4 in 2008, the last of a run of five straight wins for Super League clubs - and McDermott is delighted to be handed some home comforts.
"We'll enjoy playing at Headingley," he said. "We're in familiar surroundings and obviously the majority of the fans will be from Leeds.
"I don't think it will give us too much of an advantage. For a one-off game, these Aussie fellas will come and give it their best shot.
"If we were playing a three-game series at the same venue possibly it would have a bearing but, for one game, they'll be ready for it."
Manly hope to welcome back Australia international winger David Williams, who has been passed fit to make his comeback after missing the Sea Eagles' Grand Final triumph last October with a broken neck.
Williams, one of nine survivors from the Manly team that beat Leeds 28-20 in the 2009 World Club Challenge, is included in Manly's 20-strong travelling squad and will be named in coach Geoff Toovey's team later this week.
Toovey, who will be in charge of his first competitive match after succeeding Des Hasler in the close season, insists the Sea Eagles have no problem playing at Headingley.
"It doesn't matter where we play," he said. "I think the players will be very excited about playing in front of a hostile crowd.
"We'll really take that on board. It's a great experience for our players. Not many of our players have been over here."