Luis Mario Díaz Espinoza (born 6 December 1998) is a Costa Rican professional footballer who plays as a winger for Deportivo Saprissa and the Costa Rica national team.

Díaz started his career in the academy of his local team, A.D. Guanacasteca at the age of five, remaining with the academy until he was seventeen. In 2016, he attended a tournament with Guanacasteca in which he was noticed by Municipal Grecia, where he was subsequently signed.^[1] In the 2016–17 season, he and Grecia earned promotion to Liga FPD, the first division of Costa Rican football.^[2] Over the summer of 2018, Díaz was the subject of transfer rumors from Herediano;^[3] he would officially join Herediano for the 2019 Clausura.^[4] On July 2, 2019, it was announced that Díaz had been transferred to Major League Soccer club Columbus Crew SC for $1 million, and would join the club as a Young Designated Player.^[5][6]

Díaz made his Columbus debut on July 17 against the Chicago Fire.^[7] Coming on in the 65th minute for Eduardo Sosa, Díaz assisted fellow debutant Romario Williams in scoring a 90th-minute equalizer as part of a 2–2 draw.^[7] He was named to the team of the week for his efforts in a 3–1 victory against Atlanta United.^[8] He went on to finish the 2019 season making 13 appearances along with two goals and four assists.^[9] During the 2020 season, Diaz was part of the Columbus team that won the 2020 MLS Cup, making a total of 25 appearances for the club.^[9][10] Though Díaz was in and out of the starting lineup throughout the season, he started three out of four of the club's playoff games, including the final in which Columbus beat Seattle Sounders FC 3–0.^[10]

During the 2021 season, Díaz had a promising start, featuring in all of the first eleven games, starting ten, including in the CONCACAF Champions League. He scored his first goal in the new season against Toronto FC on 29 May, his first for the club since September 2019.^[11][12] However, an injury on national team duty led to his withdrawal from the squad,^[13] and caused him to miss three straight games for Columbus.^[14][15] After returning in time for the unveiling of Columbus' new stadium, Díaz participated in the Gold Cup with Costa Rica, resulting in his absence from the following four league games. Upon his return from the national team, he struggled to secure a regular starting position, making a total of twelve appearances to wrap up the season, with only four starts. Notably, he made a substitute appearance in the 64th minute to help his team secure a 2–0 victory against Cruz Azul in the 2021 Campeones Cup.^[16] His team would fail to make the end of season playoffs after winning the championship the previous year.^[17]

The beginning of 2022 saw Diaz relegated to the bench to start out the season, however, in the first game of the new season, he would come on as a substitute to score the third goal in a 4–0 drubbing to Vancouver Whitecaps FC.^[18] Despite initially being a substitute with occasional starts, lackluster play from his teammates, combined with his impressive two-assist game against the Chicago Fire, earned him a starting position for the rest of the year.^[19] He would go on to score the only goal in a 1–0 victory against Inter Miami CF. At the end of the year, the Crew would fail to make the playoffs for a second consecutive season.^[20]

On 5 September 2023, Díaz was waived by Columbus.^[21]

He made his Costa Rica national team debut on 6 September 2019 in a friendly against Uruguay, when he replaced Joel Campbell in the 68th minute and was cautioned in the remaining minutes.^[22]

Díaz used part of his salary in Major League Soccer to buy his family a new house in Costa Rica.^[23]

Columbus Crew

• MLS Cup: 2020
• Campeones Cup: 2021