The Belgian international had left Old Trafford to San Siro where he is on the verge of completing a £74 million move.
The Belgian striker arrived in Milan on Wednesday night and is expected to finalise his transfer over the coming hours.
Lukaku was fined by United after missing training on Tuesday. He has been maintaining his fitness level with former club Anderlecht in recent days.
United rejected a £54 million bid from Inter last month, but the Italian giants have now agreed to meet the Red Devils’ asking price.
Lukaku scored 42 goals in 96 games for United but failed to convince many supporters.
Former Man Utd captain, Neville was, however, critical of Lukaku’s fitness during his first game for United.
And now, following the news of Lukaku’s departure, Neville hasn’t held back on Twitter.
When journalist Andy Mitten wished Lukaku well for the future, Neville replied by criticising the player’s fitness and professionalism.
“Andy he admitted he was overweight! He is over 100kg! He’s a Manchester United player!” the Sky Sports pundit replied.
“He will score goals and do well at Inter Milan but unprofessionalism is contagious!”
