Ranieri's struggling Premier League champions found themselves 2-0 down in Spain but produced a spirited response.
Leicester fell 2-1 in their Champions League round-of-16 first leg at Sevilla, but Jamie Vardy's goal has given hope to the ignominious Foxes.
Goals from substitutes Marko Pjaca and Dani Alves were enough for Juventus against 10-man Porto.
Super-sub Dani Alves doubled his side's lead mere moments after stepping onto the pitch in Juve's 2-0 win over Porto.
Juventus will fancy their chance to reach the Champions League quarterfinals after a 2-0 defeat at 10-man Porto on Wednesday.
Wayne Rooney is keen to remain at Manchester United until the end of the season and help the club pursue silverware.