Marcus Rashford can rival Kylian Mbappe as one of the best players in the world within the next two years if he is "given time to learn the game a little bit more," former Manchester United forward Dwight Yorke has told ESPN.

Rashford, 23, goes into United's Premier League clash with Chelsea on Sunday on course for his most productive season, having scored 18 goals in 39 appearances so far -- four short of his return of 22 goals in 44 games last season. (His nine Premier League goals this season have an xG of 7.6, and his career tally of 53 league goals has come on 53.1 xG. While he's producing fewer opportunities, he's converting them in line with expectations.)

But despite his impressive numbers overall since the start of this campaign, the England forward has managed just four goals in 15 games in 2021 with United manager Ole Gunnar Solskjaer deploying him in a variety of positions across United's front three.

ESPN reported last month that Solskjaer and his coaches are working with Rashford to encourage him to fine-tune his finishing by developing different techniques when shooting at goal. But Yorke, who scored 29 goals in 51 games during United's Treble-winning season in 1999, said he believes that if Rashford is afforded time and patience to develop his game, he will rival Paris Saint-Germain's Mbappe as one of the world's top forwards.

"Absolutely. [Rashford] is certainly in the bracket of Mbappe," Yorke told ESPN. "The likes of [Lionel] Messi and [Cristiano] Ronaldo are a different level, but Marcus is certainly one for the future in terms of being one of the best players in the world, if he keeps working hard and developing his football.

"We haven't seen the best of Rashford yet. I think that if we give him another couple of years and let him learn the ins and outs of the game a little bit more, he will only get better. I consider that he is still in that educational part, so he has another couple of years before he develops into the complete player.

"Marcus is being Marcus, and you just see a young man who loves playing football and has unbelievable ability. He has an eye for goal and all the other attributes you look for in a striker: He's quick, he can go past people, he can create, he can score. He does all of that. We just need to allow him to enjoy it and produce that consistency. He is still in the development stage and people should just allow him to express himself so that, eventually, we'll see an even better Rashford."

In January, the CIES Football Observatory algorithm estimated Rashford to be the most valuable footballer in the world with a potential transfer fee of €165 million, with Borussia Dortmund's Erling Haaland in second position (€152m) and Mbappe (€149.4m) in fifth, by virtue of his contract being due to expire in June 2023. Despite Rashford's growing reputation, sources have told ESPN that United remain in the hunt for a centre-forward, with Haaland a top target. Earlier this week, Solskjaer refused to rule out another move for the 20-year-old, having missed out on the Norway international's signature when he left FC Salzburg for Dortmund in January 2020.

Solskjaer has used Rashford as a centre-forward in recent weeks, but he has struggled to impress in the role. Yorke said, however, that understanding of the centre-forward position takes time and some players are ultimately best deployed out wide.

"Playing with your back to goal is probably one of the most difficult positions to play on a football pitch," Yorke told ESPN while promoting #ILOVEUTD USA, a virtual fan event to be streamed on Sunday. "You are facing the other way, the opposite direction to the goal that you want to score in, so it does take a lot of speciality and know-how to play the position.

"That's why [Edinson] Cavani coming in with his experience and movement will teach these young players (Rashford, Anthony Martial and Mason Greenwood), but you need to play that position week in and week out to get better at it. You can't have makeshift strikers playing there once in a while and then going out to the right or left. It is very hard to point fingers at these young players who are asked to play different positions in the attacking third of the pitch.

"I wasn't a proper centre-forward. Andy Cole was a proper centre-forward, a No. 9, and if you look at his record for goals over the years, he has a prolific record because he only played as a No. 9.

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"He didn't play right wing or left wing, but when you are younger, in that educational phase, you tend to play left and right, and you get better over the years. But I think United have such a unique blend of young players that we should just let them go out and express themselves as best as they can, and not complicate them as much as other people are trying to do."

United travel to Chelsea on Sunday in a position of relative strength: They are second in the Premier League, 10 points behind leaders Manchester City, though with hopes of a league title fading fast after taking just nine points from a possible 18 in their past six games. Chelsea's recent resurgence under new manager Thomas Tuchel, following his appointment as Frank Lampard's successor in January, has elevated them to fifth, just six points behind United in the table.

The switch in momentum has put pressure on United to seal a positive result at Stamford Bridge to avoid being dragged into a race for the top four, but despite their recent loss of form, three-time Premier League title winner Yorke believes the club are finally back on an upward trajectory, eight years after winning their last title in Sir Alex Ferguson's final season as manager.

"We are making progress to try to win the Premier League and we have seen that under [Solskjaer]," Yorke said. "It's certainly more encouraging than what we have seen in the past, so we are all optimistic for the future with what this team can produce. There's still work to be done, but if you're looking from the outside, we are seeing the team making progress.

"It has been hard for United fans to see where the club is. We are talking about finishing in the top four, but back in the day, it was all about winning the Premier League, Champions League and FA Cup. We haven't been able to do that on a consistent basis. It has been four years now [since the club won a trophy], so hopefully in the near future, we can get closer to the Premier League and Ole and the boys can turn it around, if not this year, certainly next year."