The SPL champions travel to Juve, two-time winners of the competition, on Wednesday trailing 3-0 from the first leg at Celtic Park.
Despite the Italians' monumental advantage, Ledley has claimed that a fast start could put Celtic in a position to cause one of the biggest shocks in the history of European football.
He told reporters: "It is a fantastic arena and a fantastic team to play against and you just never know in football, anything can happen. The first half is going to be key and if we get 1-0 up then you never know.
"We know it is going to be difficult because they have been brilliant this season, we just need to, hopefully, get a good start."
No team has ever progressed from a two-legged Champions League tie having lost the first match at home by a three-goal margin.