The reigning European champions trail 1-0 from the first leg at Stamford Bridge.
With the La Liga title seemingly heading to Real Madrid following defeat in El Clasico, Barcelona are relying upon European glory to rescue their season.
"What happens against Chelsea will mark the rest of our season," Guardiola admitted to Sport.es. "Although the guys have not had long to recover, they have had setbacks like this before and risen to the challenge.
"We will see on Tuesday whether we will pass this test."
Barcelona are chasing their fifth European title.