He also played for the Birmingham Stallions of the United Football League (UFL) in 2024, leading the league in rushing yards, as well as making the All-UFL team, earning season MVP, championship game MVP, and winning the 2024 UFL Championship.

He missed his senior season of football due to a torn labrum he suffered while playing basketball.

[4] Martinez was regarded as a four-star prospect and was the seventh-highest-ranked dual-threat quarterback in the class of 2018 according to the 247Sports Composite.

[6][7] First-year Nebraska head coach Scott Frost named Martinez the starting quarterback heading into the 2018 season opener, making him the first true freshman to ever begin a season as the starting quarterback at Nebraska.

He finished sixth in the Big Ten Conference in passing yards and total touchdowns, and was fourth in passer rating.

[16] Martinez received high expectations heading into his sophomore season in 2019, earning pre-season honors at Big Ten Media Days and even appearing in Heisman Trophy candidate discussions.

[19] After a lackluster performance in the week two loss at Northwestern, head coach Scott Frost decided to start redshirt freshman Luke McCaffery in the upcoming game vs. Penn State.

[23] On December 2, 2021, Martinez entered the transfer portal with one year of eligibility remaining.

[35] On December 24, 2023, Martinez was signed by the Birmingham Stallions of the United Football League (UFL).