The Argentine coach believes he was harshly treated by Los Che and says he is hurt by the sudden nature of his departure
The 41-year-old was relieved of his position after his side fell to a 5-2 home defeat to Real Sociedad on Saturday, a result which saw them slip to 12th in La Liga.
"I just want to comment on the decision," he told journalists at a press conference. "Everyone knows that I consider it unfair and do not share it with the board.
"I think it is an irrational and hot-headed decision, but that is what you get in football.
"I want to thank the fans and the players for everything they've done. The current situation is only temporary - the team are only four or five points off their target in the league and will fight for the fourth Champions League place."
Los Che have won only five times in 14 league fixtures so far this season, but Pellegrino believes there were encouraging signs from his team before his departure.
"Obviously this is not what I want and I am hurt, but I believe this club is a work in progress," he added.
"I want to wish Valencia good luck and I hope in years to come maybe I'll get the chance to work here again."