The 22-year-old has gone on to impress with Marseille in Ligue 1 and has once again attracted interest from the Stamford Bridge outfit, not to mention Arsenal.
But Chelsea could have already got their man had they not been so insistent on managing the player's development.
The player's agent and father, Willy Ndangi, told L'Equipe: "You know how much I refused from Chelsea? A million euros (£800,000).
"About a month before Giannelli signed with Marseille, I had a meeting with a Chelsea official.
"But their people wanted a stranglehold on the player for five years.
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I did not want Giannelli to have a leash around his neck.
Willy Ndangi
"They wanted to put in place a sort of masked ownership.
"The youngster would have to have been willing to go left, right, to Turkey or who knows where.
"Like the system in place with Kondogbia, Mangala and all those others.
"The footballer must be free and have control over his career and salary.
"I did not want Giannelli to have a leash around his neck."
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