Former Manchester United captain Ashley Young believes his old club made a big mistake in selling Romelu Lukaku in 2019.Lukaku recently completed his return to the Premier League, re-joining Chelsea for a club-record fee. His move comes after two successful years with Inter Milan, which culminated in them winning the Serie A title. The Belgian attacker has proven his doubters wrong and will now aim to make a similar statement in England.Lukaku’s time with Man Utd is often looked back on as a disappointment, although his goals record was far from poor. He scored 42 goals in 96 games for the club. But they didn’t feel they got what they paid for and decided to cash in.Since then, it has been a challenge for them to fill the striker’s role. Edinson Cavani came in last season as a short-term solution and has shown his quality, committing to another year at Old Trafford.But in the future, United will likely have to spend big on another centre-forward. It is an issue they could have avoided by keeping Lukaku.One man who thinks they should never have sold him is ex-teammate Young, who has also returned to the Premier League from Inter by joining Aston Villa.After tasting success together in Italy, Young is glad to see Lukaku earning another big move.Im so happy for him, Young told The Guardian.It was the wrong decision for United to let him go. To join him at Inter and see how well he did there was fantastic.I dont know whether he thinks he has a point to prove [in the Premier League] but I dont see it like that: his record speaks for itself. He scored a lot of goals at United and everywhere else.I hope he does really well at Chelsea just as long as he doesnt turn up against Villa!In a parallel universe, Young could be playing for Chelsea too, because he revealed that Antonio Conte wanted to sign him during his time there. Instead, they ended up linking up in Milan instead.Now, though, the 36-year-old is back in his home country and ready to contribute for an ambitious Villa side.The versatile Young is willing to play wherever he is required.I think Ive played in every position in my career except goalkeeper, he said.Romelu Lukaku is now worth the biggest combined fee across a single career – who else makes the top 10?Obviously I was brought up as a winger or a No 10 and I always wanted to stay there but if youre asked to play wing-back or whatever, you go out and give your best.I have a good football brain and can play different positions. I went to the World Cup as a wing-back so you cant think that being versatile hinders your chances.Ive played at left-back in some of the pre-season friendlies with Villa and then I played as a winger in one [against Salernitana] and I scored. Wherever the manager calls on me to play, Ill go out there and give my all. There are chances to win things at this club.READ MORE: Pundit tips Lukaku, Chelsea to terrorise Arsenal star after Brentford display