Froome reportedly came down a just infection last night after arriving in Belgium ready for the race.
This is the second time the Brit has had to pull out of an event this year due to injury or illness. The first came when he couldn't take part in Tirreno-Adriatico after suffering from a back problem.
Team Sky's Doctor Richard Freeman explained they had to pull him out of today's race so he could be fit for the Tour de Romandie on Tuesday.
Freeman said, according to Cycling News: "Unfortunately Chris has been suffering from a mild chest infection.
"After an examination this morning we concluded that the best course of action would be to withdraw him from Liege-Bastogne-Liege as a precautionary measure, which will allow him the best chance of recovery ahead of the Tour de Romandie.”
Team Sky started the Liege-Bastogne-Liege with six riders instead of the maximum of eight due to illnesses and injuries and Team Principal Dave Brailsford believes all the problems seem to have come at once.
Brailsford said: "When you actually analyse and look at all of the illnesses and crashes we've had this year, we've had proportionally more than you'd expect to have and when you look at the last couple of years, we've had proportionally less than you'd expect to have.
"It's like we've saved them all up and had them at once.
“We’ve also got [Jonathan] Tiernan-Locke who’s not racing, Sergio and his cousin [Sebastian] who’ve gone back to Colombia, CJ [Sutton] had a nasty crash and had a hole in his knee, Chris is ill, Pete is ill, and before you know it, it’s the Tour of Romandie next week and the Tour of California right after that [and] you can’t start chopping and changing too much.”
Froome is set to start the Tour de Romandie and Brailsford admits he could have started the race today but if he had it would have had consequences on Tuesday.
The Team Principal said: s the reason we took him out today [from LBL], just to make sure he was ok.
“He probably could have started [Liege-Bastogne-Liege], but he probably wouldn’t have got rid of what he’s got. So you’ve got to make some calls really.”
With races coming thick and fast before the Tour de France it is crucial that Froome gets some kilometres under his belt as well as staying fit.
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