The Scottish champions are hoping to turn around a 2-0 first-leg deficit on Wednesday when they face Shakhtyor Karagandy in their playoff tie at Parkhead.
"This is one of the biggest games of my life - so much is at stake," Ledley is quoted as saying by Sky Sports News.
"So much depends on this game and there is so much pressure on myself and my teammates. Hopefully we can thrive on it and go from there."
Celtic earned around £22m from last season's competition as they reached the last 16 before being knocked out by Juventus.