But one current player - Robbie Elliot - also gave backing.
An employment tribunal on Thursday found the midfielder was ditched by the Magpies because he was diagnosed with testicular cancer.
Gutierrez, now at Deportivo La Coruna in Spain, spent seven seasons with Newcastle after joining the club in 2008.
"Yesterday they (former players) called me telling me congrats about the decision of the court," the Argentinian said on Sportshour on BBC World Service.
"I have good pals from my times over there, players that I've been playing a long period (with), like Perchy (James Perch), Ryan Taylor, (Dan) Gosling, Robbie Elliot.
"I've been talking with them, they can't understand as well the way they treat me.
"When the courts announce (the verdict) they call me and say congrats. They know (what) I had to go through, they send me congratulations for that."
Newcastle said they were "dismayed" by the tribunal's decision.