Mason Greenwood is undoubtedly Manchester United's most exciting prospect for a long time.

The youngster made his debut at the back end of last year, coming on as a 87th minute substitute against Paris Saint-Germain.

Following the departure of Romelu Lukaku, Greenwood is now United's third choice striker and has been given chances by Ole Gunnar Solskjaer this term.

And he would repay his manager's faith by scoring his first goal for the club against Astana last month.

At 17 years old, Greenwood became United's second youngest goalscorer in the Premier League era.

We've listed United's 20 youngest goal scorers ever in the Premier League, what happened to them and where they are now.

20. Phil Jones

First goal: Aston Villa 0-1 Manchester United (December 3, 2011)

Age: 19 years, nine months, 12 days

Once described as the 'next Duncan Edwards', Jones hasn't been able to fulfil his potential.

He's still at United but very much on the fringes of the first team. It will be no surprise if he departs the club in the next few months.

19. Anthony Martial

First goal: Manchester United 3-1 Liverpool (September 12, 2015)

Age: 19 years, nine months, seven days

Who could forget Martin Tyler's iconic commentary for Martial's first goal?

Martial showed wonderful skill and composure to net against United's fierce rivals on his debut.

He hasn't become the world-class player he was expected to be, but remains an important part of a Man United team that is searching for a return to the Champions League.

18. Andreas Pereira

First goal: Manchester United 3-0 Ipswich (September 23, 2015)

Age: 19 years, eight months, 22 days

Pereira went out on loan to Granada a season after scoring his first goal.

He's currently in the first team at United after another successful loan spell in La Liga with Valencia.

The Brazilian is still a fringe player, though.

17. Keith Gillespie

First goal: Manchester United 2-0 Newcastle (October 29, 1994)

Age: 19 years, eight months, 11 days

Gillespie was a promising youngster at United but was sold to Newcastle to fund their move for Andy Cole.

He went on to play for the likes of Blackburn, Sheffield United and Charlton before retiring with Longford Town in 2013.

He recently spoke of a gambling addiction he suffered during his playing days.

16. David Beckham

First goal: Manchester United 4-0 Galatasary (December 7, 1994)

Age: 19 years, seven months, five days

Beckham went on to have great success with Manchester United.

He made 394 appearances for the club and scored 85 times.

Beckham left for Real Madrid in 2003 and went on to play for LA Galaxy, AC Milan and Paris Saint-Germain.

Beckham retired in 2013 and now owns Inter Miami CF. The club will enter MLS in 2020.

15. Sylvan Ebanks-Blake

First goal: Manchester United 4-1 Barnet (October 26, 2005)

Age: 19 years, six months, 27 days

The striker made just two appearances for United but managed to score in one of them.

He went on to have a good career in the Championship where he impressed for both Plymouth and Wolves.

The goals dried up as his career went on and now, aged 33, he's playing for Walsall Wood in the 10th tier of English football.

14. Wayne Rooney

First goal: Manchester United 6-2 Fenerbahce (September 28, 2004)

Age: 18 years, 11 months, four days

Rooney went on to play 13 seasons at Man United and became one of the greatest players in their history.

He's recently played his final game in MLS with D.C United and will join Championship side Derby County as a player/coach in January.

13. Ryan Giggs

First goal: Nottingham Forest 0-2 Manchester United (August 29, 1992)

Age: 18 years, nine months, 0 days

A one club-man, Giggs played an incredible 24 seasons at United.

He went on to become an assistant to Louis van Gaal at the club but left when Jose Mourinho was appointed manager in 2016.

Giggs has been Wales manager since 2018.

12. Cristiano Ronaldo

First goal: Manchester United 3-0 Portsmouth (November 1, 2003)

Age: 18 years, eight months, 27 days)

Arguably the greatest player of all-time became a global star at United.

Ronaldo scored 118 times for United before leaving for Real Madrid in 2009. He would go on to break all sorts of records for the Spanish outfit.

Now 34, Ronaldo is still going strong at Juventus.

11. Giuseppe Rossi

First goal: Sunderland 1-3 Manchester United (October 15, 2005)

Age: 18 years, eight months, 13 days

The Italian striker left United for Villarreal in 2007, where he would become somewhat of a club icon.

He left for Fiorentina in 2012, but injuries have ravaged his career since.

Now 32, he's currently without a club since leaving Genoa in 2018. He's currently training with Villarreal but it is unknown whether he will play professional football again.

10. Adnan Januzaj 

First goal: Sunderland 1-2 Manchester United (October 5, 2013)

Age: 18 years, eight months, 0 days

Januzaj burst onto the scene with a two-goal performance against Sunderland in 2013.

But he failed to progress as hoped and left permanently for Real Sociedad in 2017.

The Belgian is now struggling for first team football, having played just seven minutes in his club's last eight games.

9. Nick Powell 

First goal: Manchester United 4-0 Wigan (September 15, 2012)

Age: 18 years, five months, 23 days

It was always going to be tough for Powell to make the step up from League Two to the Premier League.

He managed just the one goal for United, which came 10 minutes into his debut.

He's since had a decent career in the Championship with Wigan and now plays for Stoke.

8. James Wilson

First goal: Manchester United 3-1 Hull (May 6, 2014)

Age: 18 years, five months, five days

Wilson had a dream debut, scoring twice against Hull.

But he would score just twice more for the club. Wilson had numerous spells on loan including at Brighton, Derby and Aberdeen.

Wilson joined the Scottish side in the summer but is goalless in 11 games so far this season.

7. Kieran Lee

First goal: Crewe 1-2 Manchester United (October 25, 2006)

Age: 18 years, four months, three days

Another player who had a dream debut. At the age of just 18, Lee came on against Crewe and scored the winner two minutes from the end of stoppage time.

He left permanently for Oldham, where he would spend four seasons before leaving for Sheffield Wednesday in 2012. 

Lee is still at the Owls.

6. Rafael

First goal: Arsenal 2-1 Manchester United (November 8, 2008)

Age: 18 years, three months, 30 days

Rafael and his identical twin brother Fabio both joined United from Fluminense in 2008.

The more talented of the two, Rafael found first team opportunities easier to come by and scored his first goal for the club shortly after arriving in England.

The Brazilian right-back was a bit-part player during his seven season spell and left for Lyon in 2015, where he still is today.

5. Marcus Rashford

First goal: Manchester United 5-1 FC Midtjylland (February 25, 2016)

Age: 18 years, three months, 25 days

Rashford was meant to be on the bench for United's Europa League tie against FC Midtylland in 2016 but was given a start when Martial got injured in the warm-up.

And he made his mark as he scored twice in his side's 5-1 win.

Rashford has been a regular for the club ever since.

4. Kieran Richardson 

First goal: Manchester United 2-0 Leicester (November 5, 2002)

Age: 18 years, 0 months, 15 days

Richardson went on to have a good career after leaving United in 2007.

He was a decent Premier League player at Sunderland, Fulham and Aston Villa. He retired from football in 2017 after a spell with Cardiff.

3. Danny Welbeck

First goal: Manchester United 5-0 Stoke City (November 15, 2008)

Age: 17 years, 11 months, 20 days

Welbeck became a dependable player at the club before leaving for Arsenal in 2014.

The English forward has suffered a number of injuries in the past few years, which is proving to still be a problem with Watford.

2. Mason Greenwood

First goal: Manchester United 1-0 FC Astana (September 19, 2019)

Age: 17 years, 11 months, 19 days

Greenwood is United's most talented youngster at the moment.

He's showing signs that he could be a really, really good striker in the future.

1. Federico Macheda

First goal: Manchester United 3-2 Aston Villa (April 5, 2009)

Age: 17 years, seven months, 14 days

Macheda scored one of the most iconic goals in Premier League history when he scored a last-minute winner against Villa in 2009.

That goal proved pivotal as the Red Devils narrowly pipped Liverpool to the title.

But it's been downhill for Macheda ever since. After two seasons with Novara in Serie B, the Italian now plays in Greece with Panathinaikos.

So a real mixed bag there. Some players, including Ronaldo, Rooney and Giggs, went to the top of world football.

Others struggled to make their mark at the club, including Wilson, Ebanks-Blake and Lee.