The Reds travel to Tynecastle tomorrow for the opening leg, with the return match scheduled to take place at Anfield a week later.
However, Souness still expects his former club to defeat their Scottish opponents.
"I just feel Liverpool will have too much quality in too many areas and I think that will decide the tie," he said.
"Hearts would need more than half the Liverpool team to have two off nights to have a chance. There is a gulf between the Premier League in England and the SPL in Scotland right now.
"Although Liverpool aren't the force they were, they're still arguably the second biggest club in England. They're still an enormous club on the world stage so you have to respect their fantastic European pedigree."
You can read Sports Mole's preview of the contest here.