Mourinho's starting line-up against West Ham only featured two new faces but the difference from last season could hardly have been more striking. In place of ponderousness and profligacy, there was power and purpose. And in front of a buoyant Old Trafford crowd, Manchester United enjoyed their biggest Premier League win since September 2014.

Mourinho insisted there was room for improvement in his post-match press conference and he is right to be cautious, but he will also take immense satisfaction from the transformative impact of his summer signings. Nemanja Matic marshalled the midfield with man-of-the-match excellence, while Romelu Lukaku looked every bit a £75m striker as he dominated West Ham's backline.

The Belgian's goals showed exactly what he brings to Mourinho's side. For the first, he demonstrated his explosive acceleration to latch onto Marcus Rashford's reverse pass and blast a first-time finish in off Joe Hart's near post. For the second, he leapt high above West Ham's defenders to flick home Henrikh Mkhitaryan's free-kick.

United's failure to finish chances was their undoing in games such as these last season, but Lukaku didn't need a second invitation. He scored with each of his shots on target, and by the end of the game he was a desperate West Ham block away from becoming the first Premier League player since Fabrizio Ravanelli to score a hat-trick on his debut.

"There was real purpose about him today," said Sky Sports pundit Graeme Souness afterwards. "We questioned him and whether he would be able to do it every week, but he's now put a marker down. That's how he's got to be for this crowd. He was fabulous today."

Matic was arguably even more influential. The Serb had more touches, played more passes, won more duels and even completed more dribbles than any other player on the pitch. There was no goal or assist, but it was his challenge on Pedro Obiang that started the counter-attack for the first goal, and he was involved in the build-up to the fourth, too.

Perhaps the most encouraging aspect of his performance, however, was the way in which he unleashed Pogba. His discipline and defensive diligence gave the Frenchman freedom to charge forwards, and he also provided a steady supply line to his midfield partner. Over the course of the 90 minutes, Matic found Pogba with more passes (14) than anyone else.