Valladolid, who were promoted to Spain's top flight for the beginning of the 2012-13 season, were sent back down to the Segunda Division after they were beaten 1-0 at home to Granada.
The result, which secured Granada's Liga status, saw Valladolid relegated alongside Osasuna and Real Betis.
"I apologise to the club and the fans, because I didn't fulfil the task I was trusted with, after I came here last summer," said the 49-year-old.
"Obviously I'm the one with the utmost responsibility and for that, I apologise."
Martinez also admitted he was unsure whether he would be at the helm next season: "The sporting director will meet next week with the players and coaching staff. From there, he’ll inform us of his decisions."
TOPICS
LATEST ARTICLES
