Cahill has called on his side to summon the spirit of their unlikely Champions League crowning in their bid to reach the final.
Swansea have only lost twice at home this term, but having turned around their tie against Napoli and seen off Barcelona and Bayern Munich as underdogs last season, the England centre-half thinks the Londoners are well placed to overturn the two-goal deficit.
"I've found Swansea a difficult place to go," Cahill told Chelsea TV.
"On my last three visits I've had two draws and a defeat, but we proved last season in the Champions League we can do it.
"Against Napoli we were 3-1 down and we turned it around at home, so this team can do it, and we need to do it."