The Ecuador winger needed surgery to repair an ankle fracture and ligament damage he suffered in a group game against Rangers in September.
Valencia could return in time for the second leg with Marseille but has been ruled out of United's trip to the Stade Velodrome on February 23 in the first knockout round.
Ferguson said: "He's making the progress exactly the way we thought. It's looking like the end of February or beginning of March.
"He should be back training in five to six weeks time, but given the extent of the injury we'll give him more time to get into the full flow of things."