Manaj joined the Serie A outfit on-loan in August, playing 30 games and scoring five goals.
Spezia coughed up €300,000 for his 12 month deal.
But Spezia have decided they will not exercise their purchase option for the Barça striker, set at €2.7m, reports Italian transfer expert Nicolo Schira.
In the previous season, Manaj was Barca B's top scorer with 14 goals in 22 games.
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