Ferdinand watched Marseille beat Chelsea at the Stade Velodrome during the group stages earlier this season and says United must ensure they perform to their maximum when they visit in February.
"It's a decent draw," he told ManUtd.com. "They are a good team with passionate fans and it will be a hard place to go.
"We have played Lyon and Lille in recent years, so we have come across French teams a fair bit and they have always been tough games. There has never been loads of goals and I don't expect this will be much different."
Having safely negotiated their way through the group stages, Ferdinand says the next round is the time when the competition really starts to hot up.
"This is the knockout stage and this is where you earn your pennies," he added.
"We have to make sure we're right on the day. It is not a league situation. There is no chance to make up ground so we have to be ready to perform."
Rio was speaking to ManUtd.com, PA Sport, BBC Radio and Magic 1152.