The young ruckman hurt his left knee in his team's 33-point win over the Sydney Swans on Saturday night.
The Lions are hoping Leuenberger doesn't require surgery but, if he has torn the meniscus in his knee as feared, he could be facing up to three months on the sidelines.
"If he has to have surgery it'll depend on the extent of the tear, I dare say," Lions football manager Graeme Allan told lions.com.au on Monday morning.
"Best-case scenario is he plays this week. Middle-case scenario is he plays in four weeks and the worst case is 12 weeks."
The Lions may now know the extent of the damage to the 20-year-old’s knee until Tuesday.
"We're still waiting on a scan, and being Easter Monday we're struggling to get some place that's open," Allan said.
"It'll either be today or tomorrow ... the scan will either say he's right or he's wrong."
Leuenberger's potential loss would be a big blow to Michael Voss and his team, which has started the 2009 season in promising fashion.
Mitch Clark played out the fourth quarter of the win over the Swans in the ruck, and the Lions may be forced to call on the out-of-favour Jamie Charman in round four.
The Lions, who are 2-1 after three rounds, face Collingwood at the Gabba on Friday night.
Allan said exciting forward Rhan Hooper, who missed Saturday night's win over the Swans with an ankle injury, would be tested ahead of Friday night's clash with the Magpies.
