Robles was at fault for two of the three goals that Everton conceded against Sunderland on Wednesday evening.
The Toffees went down 3-0 to the Black Cats away from home at the Stadium of Light in the Premier League.
Martinez has defended 25-year-old goalkeeper Robles, and believes that he has been in very good form for the Toffees.
“He’s a responsible footballer and someone who has been in very good form,” the Everton boss told The Times about Robles. “He was down about what happened. Mistakes happen.”
Robles has kept three clean sheets in 13 Premier League appearances for Everton this season, creating 3.15 saves per game and 2.16 saves per goal on average.
The former Atletico Madrid goalkeeper is the first-choice custodian at Everton, and he will remain so next season if Martinez is still in charge of the Toffees.
Mistakes do happen from time to time, and it is great of the Everton boss to defend Robles and speak positively about him.
Everton will take on Norwich City at Goodison Park in the Premier League on Sunday afternoon.