"They had a very good Champions League campaign. They beat Ajax and Anderlecht in qualifiers and managed important results against Bayern Munich and Atletico Madrid.
"I know the coach well. The team are very defensive and physical. It's a bad draw."
Rostov, which is north east of Moscow, beat Bundesliga giants Bayern Munich in the Champions League group phase and suffered two narrow defeats by Atletico Madrid.
United play in the English League Cup final on Sunday, are still in the FA Cup and chasing a top-four finish in the Premier League. They will play the second Champions League leg at home.
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Second favourites Roma face a tricky task against French club Lyon while Schalke and Borussia Moenchengladbach clash in an all-Bundesliga derby.
Gent's reward for knocking out Tottenham Hotspur at Wembley is a tie against fellow Belgians Genk.
Celta Vigo, Spain's only survivors, face Russian club Krasnodar.
Draw for the last 16 of the Europa League:
Celta Vigo (Spain) v FC Krasnodar (Russia)
Apoel FC (Cyprus) v Anderlecht (Belgium)
Schalke (Germany) v Borussia Moenchengladbach (Germany)
Olympique Lyon (France) v Roma (Italy)
Rostov (Russia) v Manchester United (England)
Olympiacos (Greece) v Besiktas (Turkey)
Gent (Belgium) v Genk (Belgium)
FC Copenhagen (Denmark) v Ajax (Netherlands)
First legs to be played on March 9, second legs March 16
(Editing by Martyn Herman and Louise Ireland)
