While the Japanese international settles down in Glasgow, the Guinea defender Baldé is in Marseilles to complete his move to the French giants.
The centre-back, 29, became a popular figure in Scotland but many believe the time had come for him to leave after a shaky start to the season. With that deal imminent, Celtic fans have been encouraged by the impression that the former Reggina player Nakamura has already made.
Hartson said: "I know Shunsuke is a big name back in Japan, but I don't think many of the lads had heard of him at first.
"You can see, though, he has incredible vision and touch, and the fact he's done the business in Serie A - which is one of the toughest leagues for players of that type - shows he can cut it at the very highest level. He's a top-class player."
Marseilles are closing in on the deal for a player whose early season form had been a concern for the manager, Gordon Strachan, so a parting of the ways may suit all parties. Marseilles' sporting director, Jose Anigo, said: "The Baldé deal should be done. I've seldom seen somebody who has such a desire to join us.
"He knows the club and he's ready to leave the stability of a good contract in Glasgow for Marseilles. He has a strong personality and has all the essential qualities of a good defender."
Although Celtic have picked up their form in the past week, Hartson is still hurting after the early European exit."The experiences I've had in Europe with Celtic will stay with me for the rest of my life and it's massively disappointing we won't get the chance to compete in the Champions' League again this season.
"But I knew we were up against it, and I can take a bit of consolation in the fact we got a bit of pride back and showed that we'll be challenging for the domestic trophies. That's the target for everyone now."Reuse content