The Serb was removed from his position on the bench in mid-December, after a difficult opening few months at Mestalla, with Juan Antonio Pizzi now working in his place.
For Los Che’s captain, it was Djukic’s lack of push in training that was key to his lack of success.
“We are here to train and not to direct or tell a coach what to do in each session,” Costa has commented this week to reporters.
“If he sends us to run for a minute, we are only going to run for a minute. It is logical after that that everyone will do whatever it takes to work well.
“But it is very difficult when you have a person who is above you and that does not require the maximum or pretends that what you do is fine.
“Now? At the moment is who we are, in a new way of working. It is different [with Pizzi, compared to Djukic]. One imposes more rhythm and has explained more and the other was quieter and controlled and not as open to talking. The results will dictate whether a Coach is good, though.
“The working methods [now] are very good, very intense, with great joy and enthusiasm. We are starting from scratch and all are working fine each day to get the results.
“Here we will fight until the final day for the 40 points we need for the Champions League positions. Valencia is always looking for those positions.”