Under the spotlight playing against his former club Real Sociedad in the delayed 2020 Copa del Rey Final, Martínez had a major role in proceedings: he came close to scoring with a long-range shot in the first half, appeared to have conceded a penalty for handball on the edge of the penalty area at the start of the second half – a VAR review ruled this to have been outside the box – then did concede a penalty for a foul on Portu ten minutes later. He was sent off by the referee, but another VAR check decided that he had not denied a goalscoring opportunity deliberately and the red card was downgraded to yellow. The penalty was scored, and Real took the trophy with a 1–0 scoreline. In the aftermath, he was seen taking time to offer congratulations to his many old teammates and was praised in the media for his sportsmanship.