Paul Merson says Ruben Amorim's job at Manchester United could be on the line if Marcus Rashford succeeds at Aston Villa.

Rashford moved from Old Trafford at the weekend, signing for Aston Villa on loan from until the end of the season.

The 27-year-old did not feature for United since their win over Viktoria Plzen in the middle of December and was linked with a move to AC Milan and Barcelona before finally making the switch to Villa Park on Sunday.

It will be the first time Rashford has played for someone other than the Red Devils having made 426 first-team appearances for the club since 2016.

And Merson insists Amorim's job could be on the line if Rashford rediscovers his form at Villa and Manchester United, who suffered another home defeat at the hands of Crystal Palace on Sunday, continue to struggle.

"Ruben Amorim is running out of ideas at the moment," Merson told Sky Sports News. "He's struggling badly.

"What he's done with the Rashford situation is mind-blowing.

"His job is on the line at this rate. If Rashford gets 10 goals in 10 games - and Manchester United carry on the way they're playing - then the board will be asking the question: 'What are you doing?'"

Merson thinks Rashford will be determined to prove Amorim wrong and that it might prove costly for the Portuguese manager at Old Trafford.

He added: "He might be one of them where the Villa fans and the manager open their arms to him and he will go: 'I'm going to show that Amorim. You bad mouthed me, embarrassed me by saying I wouldn't get in over a 63-year-old goalkeeper coach.'

"I think he can come back. It could end very badly for Amorim - he would be under severe pressure if they keep playing badly and Rashford starts ripping it up at Villa. He won't be the Manchester United manager for long!"

Rashford was a constant feature under old boss Erik ten Hag but quickly fell out of favour when Amorim walked through the door.

He scored the first goal of Amorim's tenure in a 1-1 draw with Ipswich and grabbed a brace against Everton but was then restricted to substitute appearances before being totally left out of the team.

Rashford could make his debut when Villa meet Tottenham in the FA Cup fourth round on Sunday, and Merson believes the forward has an "unbelievable opportunity" to get his career back on track.

He said: "He's going to one of the top teams in the Premier League. Great club, great support.

"The one trick we're all missing here is he has to take his head with him. Nothing changes. It's a big gamble, a huge gamble for Amorim as well.

"But if he goes to Villa, one of the players are going to miss out - a Jacob Ramsey or so. Maybe they're alright now as Watkins is injured.

"But if this doesn't work, it's wow - £300,000 a week. I just worry that it's been a long time for him, you can't just turn it on like a tap. There have been problems.

"I hope he gets it sorted for Villa and the lad's sake - because his career will finish quickly if it doesn't. He's been given an unbelievable opportunity at a great club and he has to take it. It's not the case of turn up, different shirt, it will be alright. I don't know about it, I hope they do get it right."

Meanwhile, Rashford says Aston Villa's "constant ambition" attracted him to the club and he hopes to rediscover his form at Villa Park.

The 27-year-old admitted Villa's ambition and the prospect of playing in Europe's top competition was what convinced him to make the switch to Birmingham.

In a first interview, he told Villa TV: "Definitely excited. It's an ambitious time for this club and a great opportunity for me to join this team and help them keep pushing forward. I'm excited and can't wait for the first training session and game.

"[Unai Emery] is a top manager and what he's done for the club since coming in is unbelievable. It's their constant ambition which is attractive and why you want to join such a club. You want to keep improving year on year and that's what the team's been doing and doing this year.

"They are still in the Champions League and we want to go as far as we can in that and if you don't aim to win it, you'll never win it so that will be my main objective and keep pushing in the league to get as high as possible.

"This is my first time playing for any other team so you don't know what to expect but it's been more excitement, not scared of going into a new environment so it's all been exciting but with them lads [Ollie Watkins and Ezri Konsa from England] being there it's good."

Rashford could make his debut when Villa meet Tottenham in the FA Cup fourth round on Sunday.

Asked why he wanted to join Villa, he said: "They're a club that's in a good position in the league and pushing to get higher. Still in the Champions League, good manager, ambitious manager, great talent in the squad.

"I've had to choose somewhere where my style of football is suited and can help them and help me rediscover and improve as a player, its only short term and I want to make the most of my time here.

"The biggest competition for the club to be involved in and always great nights so it'll be a new experience for me playing for Villa in the Champions League but like I said it's always going to be a great moment but the aims will be the same - to try our best to win it."

Sky Sports' Gary Neville:

"He had to get out of the club. He's been battered in the last few weeks by his manager. That's the only person who matters in football, your coach, and I think some of the statements from Ruben Amorim towards Marcus Rashford have been brutal, emphatically saying that he doesn't want him. I don't see how there's any way back after the comments that he's made.

"There are a number of things that are in his favour at Villa. He's going to a far better team at this moment, he's going to a coach who's world class, which is a real opportunity for him.

"It puts pressure on Marcus to perform for Unai Emery because if you don't play for him, then you're sort of saying Ruben Amorim might be the problem, Erik ten Hag might be the problem. Unai Emery can't be a problem for Rashford. He has to play well for him.

"The other thing is the style of play. How Villa play I think could suit Rashford as well. Maybe the spotlight won't be quite on him as it was at Manchester United but certainly there'll still be a lot of attention. Villa are in lots of competitions, they've still got a lot to play for and it's a real opportunity for Marcus.

"It absolutely sounds like what he needs. The last thing that I would think Rashford needs at this moment is someone just saying, 'go and enjoy yourself'. He needs to have some discipline in his game, he needs to be coached and he needs to make sure that the team know exactly what it is that they want from him.

"Unai Emery will do that, he's an absolutely amazing coach. It's exactly what Marcus Rashford needs and what he's got to do is buy into it."