MANCHESTER -- Jesse Lingard has warned Premier League and Champions League defences that Marcus Rashford is only getting stronger and faster.
Rashford has made a flying start to the new season with four goals in eight games for club and country.
Jose Mourinho said in the summer the 19-year-old was set for a "big season" in his second full campaign in United's first team.
Mourinho revealed during preseason that Rashford, who scored on his Champions League debut against Basel on Tuesday night, has already shot up 3 centimetres since he took over as manager.
And Lingard says defenders at home and abroad should be worried.
"He's got a lot bigger, a lot quicker, and he's focusing on goals and assists which is the main aim," Lingard said.
"If he can carry this form on now the rest of the season it will help us a lot. He's going to stay grounded because he's a grounded kid."
While Lingard has watched his friend Rashford play a key role for Mourinho this season, the midfielder has had to wait for his chance.
The 24-year-old is yet to start a game after being substituted at half-time during the 2-1 Super Cup defeat to Real Madrid.
Mourinho is set to rotate is squad for the Carabao Cup tie against Championship side Burton Albion next Wednesday and Lingard accepts he will have to wait his turn.
He said: "There's a lot of games, especially this month, so you're always going to get your chance. I've just got to be patient and when you come on the field you want to make a difference.
"You learn a lot and you want to keep training hard and like I said you will get your chance, it's all about taking it.
"Of course it's always going to be difficult if you're not in the team but as long as you train hard there's a lot of games coming up and you know you'll get a chance."
Before beginning their defence of the League Cup against Burton, United face Everton in the Premier League on Sunday in what is set to be Wayne Rooney's return to Old Trafford after leaving in the summer.
After departing as the club's record goal scorer, Lingard is sure Rooney will be well received by the fans.
He said: "he's always going to be recognised as a legend at the club and he'll get a great reception when he comes back.
"His experience in games, especially when you're young and if it's only 1-0 it's always hard to manage a game, and he knew what to do at times especially towards the end of games. You learn every day off him.
"Obviously he was at Everton as a young boy and he thought it was the right decision at the time."