Louis van Gaal’s surprise inclusion of Januzaj, who made his first start since February, was vindicated on 29 minutes when the young Belgian opened the scoring with a deflected low finish.
Villa had stood toe-to-toe with United in an uneventful opening half hour at Villa Park as both sides struggled to retain possession or mount a sustained assault on the opposing team’s goal.
The inclusion of Rudy Gestede on the hour mark threatened to haul Villa back into the game, but United stood firm as they extended their unbeaten run at Villa Park in the league to 20 games with their second successive 1-0 win of the season.
Villa entered the first top-flight game held on a Friday night since 2004, unchanged following their opening day victory at newly-promoted Bournemouth while Januzaj’s inclusion saw Ashley Young start the game on the bench against his former club.
United had the first opening of the game on 16 minutes when Morgan Schneiderlin ghosted into the back post to connect with Memphis Depay’s, but he could not steer his effort on target.
Brad Guzan crashed into a Memphis to stop him from latching onto Juan Mata’s through ball on 20 minutes, as United began to take hold of the game.
And the Reds were soon in front as Januzaj collected Mata’s incisive pass, cut inside Richards’ sliding tackle before sending a low drive in off the post, via a deflection off Villa defender Ciaran Clark.
Villa saw claims for a penalty waved away shortly before half time as Matteo Darmian and Richards tussled in the United area, but referee Mike Dean was unmoved.
Jordan Ayew shot over two minutes after the break when a sloppy Mata pass gifted him possession, but United ‘keeper Sergio Romero remained untroubled between the sticks.
The hosts then mounted a sustained push to get back into the game, with Gabriel Agbonlahor testing Romero with a header.
Bastian Schweinsteiger and Ander Herrera were then brought on, swinging the game back in favour of the visitors despite Gestede entering the fray.
United had lost their first-half fluency, a testament to Villa’s increased efforts in midfield, although hardly looked in danger of losing their lead.
And they had the chance to wrap up the game on 73 minutes when Mata produced yet another defence-splitting pass to put Memphis through on goal, but the Dutchman’s curling effort went agonisingly wide off Guzan’s goal.
Villa failed to take advantage of their reprieve as United coasted to victory in the rare Friday night outing.