United picked up a 2-0 win on their first trip to the Eastern European country.
Newsonline report that first-half goals from Jadon Sancho and Cristiano Ronaldo saw Erik ten Hag’s side bounce back from their defeat against Real Sociedad in the competition.
However, it has now emerged that at least 12 members of the squad began to feel ill upon their return on Friday morning.
United flew back to the UK on a private jet after the game, but yet still picked up an unknown illness, which is believed could have come from something they ate, or from the plane itself.
READ ALSO EPL: Leicester Identify Two Managers To Replace Brendan Rodgers
A few players missed the scheduled recovery training session on Friday at Carrington, while some were still too unwell to turn up the following day.
Thankfully for Ten Hag, he did not have to prepare the team for the home match against Leeds United, which was originally scheduled to take place on Sunday.
The game was postponed due to a lack of available police ahead of the Queen’s state funeral on Monday at Westminster Abbey.
