Zlatan Ibrahimovic's close-range header secured Manchester United a much-needed win from a flat Europa League clash with Zorya Luhansk.
Two weeks on from opening their maiden group stage campaign in the competition with defeat at Feyenoord, Jose Mourinho conceded his side could ill afford to falter against Thursday's relatively unknown Ukrainian opponents.
Zorya certainly played their part at Old Trafford and frustrated the hosts for large parts, but Ibrahimovic's close-range header would eventually secure a 1-0 win that may not have enthralled but kick-starts United's Group A campaign.
"It was difficult, we had chances in the first half but we didn't take them and they were organised with people behind the ball," Mourinho said.
"(In) one week (we had) three defeats, one week (we have) three victories. I was not depressed with the defeats or on the moon with the victories. The game on Sunday is now the most important."
Zorya were proving a nuisance on the break but struggling to threaten Sergio Romero's goal, with United snatching a winner two minutes after Wayne Rooney came off the bench.
The England captain's mishit effort was headed home by Ibrahimovic, securing an important three points from an uninspiring match.
The big talk pre-match was captain Rooney's place among the substitutes for a second successive match, watching from the dugout as his team-mates struggled for consistency in a tame opening.
Half-time allowed the Ukrainian visitors to settle and they returned strongly, with Olexandr Karavaev's fine cross just evading Zeljko Ljubenovic.
United's own attempts to create an opening down the flanks were coming to nothing, leading to Rooney's introduction shortly after Zorya substitute Paulinho got away a curling effort from the edge of the box that a diving Romero palmed away.
The 67th-minute introduction was followed by a goal within two minutes, leaving those around Old Trafford breathing a sigh of relief.
Neat play down the right ended with Timothy Fosu-Mensah pulling back for Rooney. While the substitute could only hit his effort into the ground, it threw Zorya's goalkeeper off balance and Ibrahimovic rose to power home a close-range header.