Ronny Johnsen explains how Romelu Lukaku's addition has transformed Manchester United this season

Former Manchester United star Roony Johnsen has heaped praise on Romelu Lukaku and explained how his addition to the squad has transformed Jose Mourinho's side this season.

The Red Devils are undefeated so far in all competitions and dropped points against Stoke City and Liverpool in the league. They progressed to the fourth round of the Carabao Cup and will face Swansea City in the cup competition.

Zlatan Ibrahimovic led the Red Devils' attack last season. He scored 28 goals in all competitions for the Old Trafford club as they went on to win the EFL Cup and the Europa League in the 2016/17 season.

The Swedish striker suffered an injury in April and is still recovering. United signed Lukaku from Everton in the summer and has already been in fine form for the 20-time English champions.

Johnsen was part of United's treble winning side in the 1998/99 season. He says the arrival of the Belgium international has seen Mourinho's side stretch the opponents, which has been vital in their impressive start to the campaign.

"He has been a revelation since he came to Manchester. When he came in, we started to stretch the teams. We need players to stretch the opponents and make sure the space in the midfield is getting bigger," Johnsen told IBTimes UK at an event organised by Apollo Tyres, who are United's official tyre partner.

"He is also a tremendous goalscorer. It's lots of things with Lukaku coming into the team, not just because he is a goalscorer, but he also stretches the team.

"As a defender, it is easy to play defence if you know the opposition plays short all the time. But now, you can have the ball over the defender's head and that makes it much more dangerous. You step off a little bit, which makes it easier for other players as well."

Lukaku scored on his United debut in the Uefa Super Cup defeat to Real Madrid. Since then, he has scored 11 goals in 11 matches played in all competitions and out of those matches, the 24-year-old has failed to score only twice this season.

Johnsen believes his goal against the Champions League winners took the pressure off his shoulders to perform at Old Trafford.

"It seems like relations within the team are positive. I had a good belief when I heard for the first time they might sign him because of what he has shown at Everton," the Norwegian said.

"Sometimes, players need time, but that was not the case with Lukaku. It is all-important for people up front to score goals.

"Sometimes they go into a shell and don't score. He scored immediately and that took away all the pressure off his shoulders. You see the width of the game more now than was the case last year."