[1] Martínez reached the third round of the 2021 Australian Open in singles for the first time at this Major, defeating Emil Ruusuvuori, his second showing at this level in his career.

They defeated the 14th seeded Belgians Sander Gillé/Joran Vliegen in the third round and the pair of Rohan Bopanna/Franko Škugor in the quarterfinals.

They entered the tournament as a replacement alternate pair for the top seeds Nikola Mektić/Mate Pavić.

Martínez reached his first ATP final at the 2021 Generali Open Kitzbühel where he was defeated by Casper Ruud.

[1] At the 2021 Kremlin Cup he was defeated by Marin Čilić in only the second quarterfinal of the season and third in his career at ATP level.

[1] Martínez participated for the first time in the 2022 ATP Cup as part of the Spanish team where he played doubles with Alejandro Davidovich Fokina (won both matches) and Albert Ramos Vinolas (lost both matches) and helped Spain reach the final.

Martínez reached the third round of the 2022 Australian Open in doubles for the first time at this Major partnering compatriot Pablo Andujar.

After receiving a first round bye, he defeated Jaume Munar, Yannick Hanfmann and Alejandro Tabilo to reach his second ATP final.

[7] He reached the third round of a Masters 1000 for the first time in his career at the 2022 Miami Open defeating Jan-Lennard Struff and upset 27th seed Cristian Garín.

[1] At the 2022 Rakuten Japan Open Tennis Championships he reached the quarterfinals for a second time at an ATP 500 tour-level, defeating Alexei Popyrin and Jaume Munar.

[8] As a result of a couple of first round losses in the beginning of the season, his ranking fell outside the top 100 after the 2023 Rio Open and as low as No.

At the 2024 Estoril Open he reached his fourth career ATP semifinal defeating Daniel Altmaier compatriot Roberto Bautista Agut and lucky loser Richard Gasquet.