After initially playing as a central defender in his youth, Martínez later established himself as a forward, citing Radamel Falcao as one of his major influences. A dynamic, quick, agile, and technically gifted player, who is a prolific goalscorer, he is known for his elegant playing style, good dribbling skills, and clinical finishing ability, as well as surprising physical strength and aerial prowess despite his diminutive stature; however, he has also drawn criticism from pundits for his lack of accuracy from the penalty spot. Possessing good link-up play, defensive contribution, and an ability to drop deep off the ball to either press opponents or drag them out of position, he is also a highly creative and hard-working player, who is capable of assisting goals as well as scoring them himself; as such, he is also able to play as a second striker, in addition to his usual role as either a centre-forward or out–and–out striker. Due to his leadership, tenacity, and mentality on the pitch, he has been nicknamed El Toro (“The Bull,” in Spanish). In 2020, Spencer Rance of 90min.com considered Martínez to be one of the most promising young players in world football, while manager Mauricio Pochettino rated him as one of the best strikers in the world. Former Argentina and Inter striker Hernán Crespo likened Martínez to compatriot Sergio Agüero in 2020.