The American wonderkid has been linked with a move to Old Trafford in recent times while Liverpool also seem to be interested in the attacking midfielder, having had a £35m ($48m) approach rebuffed in 2016.
While the 19-year-old playmaker has scored just three goals and provided one assist in 16 league games this season for the struggling Bundesliga side, his stock remains high as ever as one of the most promising youngsters in world football.
Seen as the future of American football, having become the youngest player to win the "US Soccer Male Player of the Year" award in December, Pulisic also comes with huge marketing potential due to his nationality.
With the Red Devils reportedly monitoring the teenager, Nicol believes it is inevitable that Pulisic will become a United player, but has warned him to stay at Dortmund for at least another year.
"Again this would be down the line," Nicol told ESPN FC via Express. "I think Pulisic is a sensible kid, he's only just now a regular at Dortmund. I think he needs to stay there for another 12 months anyway.
"Now, does he go to Man United eventually? I think definitely there is a possibility of this being a hit. The kid I think is going to be good enough, I think he's going to develop into a world-class player.
"And from a commercial point of view for Manchester United, I think this is a no-brainer. I think we're talking 18-months time from now, there's a real possibility Pulisic goes to Manchester United."
Pulisic will notably have to wait until Qatar 2022 to make his first World Cup appearance, following the USA's failure to make the 2018 World Cup in Russia.
His current Dortmund deal expires in 2020, having signed a contract extension in January 2017.