But Eddie Howe knows his side will face a 'challenge' against the current Belgian Pro League leaders, who won 3-1 away at PSV in their first ever Champions League fixture two weeks ago.
Wednesday's game will be played at Anderlecht's Lotto Park, and Howe's side will train there on the eve of the match.
Before that, Howe addressed the media inside the bowels of the stadium and here are some of the main talking points from the United head coach's pre-match media briefing on Tuesday:
On Union Saint-Gilloise...
"They've started the season very, very strongly and they had a great result in the Champions League against PSV. They're tactically interesting, they'll give us a physical threat as well. They've got two big strikers. I've been very impressed by watching them play.
"We know it'll be an important game on our Champions League journey but it's going to be a tough one. This will be a good challenge for us at a time in the season where we know we need to perform."
On the team's journey to Brussels...
"The journey was good - it was a very quick flight for us. We'll train this afternoon and the squad is in a pretty good place, minus Tino (Livramento). We're still awaiting feedback on the extent of his injury but apart from that we're okay.
"(Fabian Schär) is back in the squad."
On team-news...
"We'll make a decision after training on how all the players look physically; Arsenal was another really physical game for us, a tough game mentally, but physically it was a big output game for us so we'll try and make the right decision in terms of team selection to make sure everyone's fresh."
On Nick Woltemade, who has scored twice in three starts for United...
"Great to see him score with his head. As I said when we signed him, we know he's a big player and that has to be a source of goals for him, with the height that he brings, and it's something we felt we could improve.
"But the two headers are all his own work and he deserves the praise for them because they're two outstanding moments and it shows that hopefully, once the team services him and gives him better balls in and around the box, there's other ways he can score as well. But that's certainly a promising start."
On training at Lotto Park...
"I think it all depends on lots of different things, like the journey time, how we feel about the certain training sessions, how much we want to give away on our preparation.
"We felt coming here that getting to know our surroundings was more important so I think it'll be an important training session for us with the pitch and the stadium. Travel time's been minimal so we've got here early, we'll settled and hopefully that'll help our performance."