Romero was born on September 9, 1996, in Camarillo, California, the eldest of three children. He cites his experience watching his father play in a Southern California baseball league as inspiring him to take up the sport.[1] He is of Mexican descent, and got his nickname from his grandfather who couldn't pronounce his name in English.
In 2017, Romero played for the Lakewood BlueClaws and Clearwater Threshers. After posting a combined 10–3 (W–L) record, with a 2.16 ERA, and 128 strikeouts, he was named the Phillies’ minor league pitcher of the year.[7] Showing a glimpse of Romero’s enormous promise, on May 10, 2017, he threw eight one-hit innings against the Greenville Drive, in a BlueClaws home victory at FirstEnergy Park.[8]
In 2018, with the Reading Fightin Phils, Romero was 7–6 with a 3.80 ERA, with 100 strikeouts in 106.2 innings.[9] He was selected to play in the Arizona Fall League for the Scottsdale Scorpions following the 2019 season.[10] On November 20, 2019, Romero was added to the Phils’ 40–man roster.[11]
Philadelphia Phillies
On August 21, 2020, with the Phillies playing a road game in Atlanta, Romero made his big league debut. He pitched the eighth inning, with the Braves ahead 11–2. Romero struck out all three batters that he faced.[12] Romero finished his rookie season with a 7.59 ERA in 12 appearances.
On May 19, 2021, it was announced that Romero would undergo Tommy John surgery, ending his 2021 season.[13] In 11 games, Romero recorded a 7.00 ERA with 8 strikeouts.
On July 15, 2022, Romero was activated from the injured list to make his return from surgery.[14]
St. Louis Cardinals
On July 30, 2022, Romero was traded to the St. Louis Cardinals in exchange for infielder Edmundo Sosa.[15] Romero pitched in 15 games for St. Louis down the stretch, recording a 3.77 ERA with 16 strikeouts in 14.1 innings of work.
Romero was optioned to the Triple-A Memphis Redbirds to begin the 2023 season.[16]