The Swansea-born striker feels 'really sorry' for the 29-year-old.
Indeed, the Swansea-born striker - now a pundit with the BBC - believes the forward was 'unplayable' at his best and a cult hero among the Swans' faithful.
Now, however, the Spaniard looks set to leave Swansea, with boss Garry Monk recently being quoted by the BBC among others as saying he does not believe Michu will play for the Welsh club again.
It's something Hartson can't quite explain - but it is something that irks him considerably, as Michu has virtually gone from hero to zero overnight.
He told Kicca: "News that Michu’s career is over at Swansea is a classic case of a player going from hero to zero.
"He was totally unplayable. He started scoring from day one and scored important goals against the top sides - including Chelsea and Arsenal.
"That is why it is such a terrible shame his career at Swansea now seems to have come to an end. I really feel sorry for Michu because there seems no obvious reason why it went so wrong.But mostly I feel sorry for the fans."
A bizarre case?
Michu's Swansea decline, as Hartson is at pains to point out, is quite unexplainable. The Spaniard went from the Welsh side's outright hero to someone with no future at the club rather suddenly.
Where the 29-year-old was putting Arsenal's defence to shame, he will now likely not even play against another Premier League defence.
As for Swansea on the whole, the club are going from strength to strength and the case of Michu appears to be a bizarre one - but one they simply have to live with and move on from.