In the aftermath of a couple of dramatic VAR interventions, the Portuguese scored the only goal of the game to hand his side their first Premier League home win of the season.
West Brom started the game on the front foot and looked the more resolute side defensively, although they needed Sam Johnstone to come to their rescue at times. The likes of Anthony Martial and Marcus Rashford came close to scoring, but neither side was able to disturb the scoreline.
The Red Devils lacked the creativity and, at some points, fared worse than their counterparts. However, a win was all they needed after the enervating international break to move up to ninth in the table.
The Baggies, despite a motivating performance, remain winless since securing promotion.
On that note, we list the five major talking points from Manchester United's 1-0 win over West Brom.
#1 West Brom begin fearlessly, Manchester United test Johnstone
Apart from a jinking run from Martial in the early stages, it was all West Brom. The visitors had plenty of the ball, with United visibly looking frustrated.
The likes of Grady Diangana and Conor Gallagher looked threatening in the advanced areas of the pitch, but a 16th-minute save from Johnstone was what ignited Manchester United's staging.
On the back of some lovely work from Fernandes and Rashford, Martial sidefooted an effort to test the palms of the West Brom shot-stopper.
Karlan Grant came close to breaking the deadlock from what was perhaps West Brom's finest passage of play. His swiftly-driven shot deflected wide of the far post.
#2 Slaven Bilic heads into half-time as the happier boss
West Brom portrayed glimpses of their technical brilliance on both ends of the pitch.
While they were clearly the better-drilled outfit, Gallagher and Grant were also exploiting gaps between the red shirts quite fluently.
Manchester United, on the contrary, couldn't translate their possession to repeated chances. Although they called the opposition goalkeeper into action, it was far from the dominance they should've boasted at home.
Indeed, they went over six hours without scoring a league goal at Old Trafford, whereas West Brom, for the first time this season, did not trail heading into the break.