Paolo Cannavaro and Gianluca Grava were cleared of failing to alert authorities to a potential fix, so their six-month bans were wiped out and a two-point penalty quashed.
"First of all, I am very happy for Paolo and Gianluca, who are two lads with exceptional values," Mazzarri told the official club website.
"They had a terrible Christmas and were the victims of huge injustice. Naturally, I am also happy with our position in the table.
"We earned those two points on the pitch and it would've been another injustice if they had been taken away from us."