Former Manchester United winger Andrei Kanchelskis warned the Premier League giants against complacency in next week's Europa League last 16 first-leg clash against unfancied Rostov.
Last year's Russian league runners-up are competing in their first full season in Europe and claimed a stunning victory over Bayern Munich in the Champions League group stages before dropping down into the Europa League.
They have lost just once in their past seven European home games -- a 1-0 defeat to Atletico Madrid in October -- and recorded a thumping 6-0 win at Tom Tomsk on Friday in their first game after the long domestic winter break.
"Rostov have played just a few matches against Europe's top clubs but in the upcoming match Man United will discover what it feels like to come up against a really well-organised team," Kanchelskis, who won back-to-back titles with United in 1993 and 1994, told Sport Express daily.
The ex-Russian international believes Rostov have little chance of pulling off an upset with United boss Jose Mourinho chasing the only European trophy that still eludes the English giants.
"Any trophy matters. Only fools can say that the Europa League is not important," he said. "There is no doubt that Mourinho understands clearly that the more trophies he wins the more authority he gains.
"Of course Rostov have a chance to advance. But their hopes are slim, Manchester are clear favourites."
Rostov were founded in 1930 as the team of a local factory churning out agricultural machinery during the early days of the Soviet Union.
After years of playing in the Soviet lower leagues, they won promotion to the Russian top flight in 1992, just after the fall of the USSR.
The club was renamed FC Rostov in 2003 following decades as Rostselmash and won their only trophy in 2014, when they beat Krasnodar in the Russian Cup final on penalties.
"It will be very interesting to play Man United," Rostov's Romanian midfielder Andrei Prepelita told UEFA.com.
"They have top players and a top coach, but we also performed well in Europe this season and beat Bayern Munich. It's nice to start at home. Hopefully, the Russian frost will help us."
The club's set-up is an intriguing one with Kurban Berdyev, the man who led Rubin Kazan to back-to-back Russian titles in 2008 and 2009, still a figure of considerable authority despite stepping down as manager last year.
He was subsequently appointed vice-president and continues to oversee training, while assistant coach Dmitry Kirichenko takes charge from the dugout during matches.
Despite being officially in charge, head coach Ivan Daniliants is largely responsible for carrying out the team's media duties.
- Security fears -
The game in Rostov has unsurprisingly raised security concerns with English and Russian fans set to cross paths for the first time since clashing at last year's European Championship in France.
A documentary aired by the BBC last month, entitled "Russia's Hooligan Army", showed Russian fans predicting further violence between supporters at the 2018 World Cup in Russia -- especially targeting British fans.
But Rostov officials dismissed fears of hooligan attacks against visiting fans in the southern Russian city and guaranteed full security for travelling supporters.
"We expect around 300 United supporters to attend the match and I can assure them they have nothing to worry about," Viktor Kuleshov, Rostov's head of security, told AFP.
"We have not planned any extraordinary (security) measures. No incidents with the visiting fans took place at our previous European home matches and we do not expect any problems on Thursday.
"Nevertheless we increased the number of stewards at this match and will set up some additional buffer zones between the visiting fans and Rostov supporters."