In one of the most high-profile switches of the January transfer window, the Chilean forward joined the Red Devils from Arsenal, with Henrikh Mkhitaryan heading to the Emirates Stadium.
Speaking about his new forward partner, Lukaku said he wasn't surprised to see Sanchez end up with United, per Sky Sports:
"He [Sanchez] is a Manchester United player—he was destined to play here. He deserves to be on the big stage. It was something he wanted as well.
"He has a lot of experience after playing for Barcelona and Arsenal. I admire the quality he has on the ball, but especially his will to win. People were criticising him for being moody, but he is not like that. He is a just a winner."
Sanchez has featured twice for United since arriving, helping the team to a 4-0 win in the FA Cup against Yeovil Town on his debut. The forward could then do little as the Red Devils were well beaten in the Premier League by Tottenham Hotspur in midweek.
Having slipped into something of a comfort zone at the Emirates Stadium previously, Paul Hayward of the Daily Telegraph said Sanchez may take a while to get up to speed at United:
The forward is poised to make his first appearance at the Theatre of Dreams on Saturday, as United face an out-of-form Huddersfield Town.
For Sanchez, it's an ideal opportunity to get his goalscoring up and running in the colours of his new club. However, there aren't many associated with the Red Devils that have any doubts about the team's new No. 7 being a huge success.
After all, the Chilean has been sensational for the Gunners during his time in the Premier League, creating goals and taking chances with remarkable regularity.
As noted by Match of the Day after Sanchez's switch to United was confirmed, the forward is an all-round contributor:
While Sanchez is a versatile player, it'll take some time for manager Jose Mourinho to find a formula for getting the best out of the 29-year-old.
The former Arsenal man can play on either flank and in support of a centre-forward. He also showed for the Gunners last season that he can be effective at the point of the attack—a position typically occupied Lukaku.
"It is the manager's choice [if I am picked], but he knows what I can do for the team—I score goals and give assists and I think in my short time here I have been important for the team," said the Belgian of potential competition for his place.
Journalist Daniel Harris suggested United may benefit from the Belgian being taken out of the side:
Sanchez gives the Red Devils a wonderful option in the final third, but if United are going to get the best from Paul Pogba in a three-man midfield, only a trio of positions are left to occupy higher up the pitch.
Lukaku and Sanchez are both excellent footballers, and if they do strike up an understanding, they have the potential to be devastating. Mourinho will hope to see some sort of affinity forming in the weeks to come.