The Blues host the Ligue 1 champions in the second leg of their last-16 clash at Stamford Bridge on 9 March.
PSG hold a slender 2-1 lead after Zlatan Ibrahimovic and Edinson Cavani beat Chelsea goalkeeper Thibaut Courtois in Paris.
Laurent Blanc’s side are a staggering 24 points clear at the top of Ligue 1 and haven’t lost a top-flight game so far this season.
Chelsea, meanwhile, are in 12th place after a disastrous attempt at defending their Premier League crown.
Former Manchester United captain Keane is under no illusion which club will book their place in the Champions League last-eight draw.
“They’re building nicely,” Keane told ITV Sport.
“Chelsea haven’t been at their best and inconsistent this year. I’d go with PSG on that one.”
Chelsea won the Champions League for the first time in 2012 after a penalty shootout victory over Bayern Munich at the Allianz Arena.
PSG have never won Europe’s top prize since the Champions League’s inception in 1992.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news