Memphis Depay scored a first-half double and provided a late assist for Marouane Fellaini to lead the English club to a 3-1 win over FC Brugge in the first leg of their Champions League playoff.
Playing his third match in United's iconic number seven shirt, the Netherlands winger rescued his new club from potential embarrassment after the Belgian side took a surprise eighth-minute lead through an own goal by Michael Carrick.
Depay equalised five minutes later with a low shot and gave United the lead with a curling shot from 20 metres in the 43rd.
Bruges had defender Brandon Mechele sent off in the 80th for two bookings, before Depay whipped in a cross that substitute Fellaini headed in with virtually the last touch of the game.
Elsewhere, Islam Slimani struck a late winner as Sporting Lisbon defeated CSKA Moscow 2-1 in their first leg.
Slimani stroked the ball past CSKA goalkeeper Igor Akinfeev in the 82nd minute after a one-two with Andre Carrillo, who fed the ball to the Algerian with an elegant backheel.
Earlier, Sporting had taken the lead in the 12th minute. CSKA's Seydou Doumbia sent the game into halftime at 1-1 after bursting in behind the Sporting defence for a 40th-minute equaliser.
FC Astana 1-0 Apoel Nic
BATE Bor 1-0 Partizan Belgrade
Lazio 1-0 Bayer Leverkusen
Man Utd 3-1 Club Brugge
Sporting CP 2-1 CSKA Moskva