"Panathinaikos FC announces the termination of its cooperation with coach Fabriciano Gonzalez and his assistant Ferreira King by mutual agreement," the club said in a statement on their official website.
"The club would like to thank both men for their help at a very crucial time for the club and wishes them the best of luck in their careers. The new coach until the end of the season is Giannis Vonortas.
The 52-year-old Polish-born Vonortas, the Greens' fourth coach of the campaign following Jesualdo Ferreira, Juan Ramon Rocha and Fabri, was a former Panathinaikos player and had been coaching the academy side. He also worked as assistant to former first-team coach Rocha.
Fabri's fate was sealed after the Spaniard launched a stinging verbal attack on the club's players following a disappointing 1-0 home defeat to top-flight newcomers Platanias on Saturday.
That result left the Athens club in sixth place, three points behind PAS Giannina, who occupy the final place for the play-offs which decide the European places at the end of the regular season.
The 57-year-old, who has become well known for his animated touchline antics and sharp comments during his short time in Greece, heavily criticised the players in his news conference, suggesting some of his squad "did not have the balls" to wear the shirt.
"In this Panathinaikos squad there are players who do not have the blood or the balls to wear the shirt," he said. "We need to see who can keep wearing it - some players went out on the pitch without understanding what exactly the team is playing for.
"I am very upset. Managers have to analyse the situation and see who deserves to stay in the team; to hit his hand on the table and make decisions. This is my opinion. I'm talking about all this now because I remained silent in the past. I tried to be polite as far as I did after the match with Mars. It's time to see things clearly."
Fabri's outburst has reportedly provoked anger among the players, none of whom gave any interviews after the match.
The national sports press on Sunday all ran with stories saying that Fabri would be jettisoned by the club and that Vonortas would take charge until the end of the season.
Fabri, whose full name is Fabriciano Gonzalez Penelas, replaced Argentinian Juan Roman Rocha on January 8 but the club have struggled with indifferent form amid a background of financial problems.
To make matters worse, arch-rivals Olympiacos have already wrapped up the title with the Greens an astonishing 34 points behind after experiencing what will go down in history as their worst season on record.
Their previous worst performance came in 1980-81 when the team collected 13 victories. This season the Greens have only picked up nine wins with only three matches to play.