Evans was forced off during the 2-1 win in Romania, after initially picking up the problem against Tottenham Hotspur last weekend.
Ferguson admitted that given United's current injury situation he will be forced to sweat on Evans's fitness for the trip to Newcastle United on Sunday, October 7.
The United boss said: "Jonny got injured on Saturday& he had a recurrence of that.
"It is a dead leg. He has five days to recover for Sunday. Hopefully he will be okay."
United already have a number of players sidelined, including Serbian centre-back Nemanja Vidic with a long-term knee problem.