The 2018 season marks Mateo's 8th season in professional baseball.

Mateo was signed as a 21 year old international free agent by the New York Mets in 2011. Mateo began his career as a starting pitcher, going a combined 10-6 in 25 starts with an impressive 2.25 ERA while racking up 165 strikeouts to just 14 walks in 136 innings pitched in his first two seasons. For his efforts, Mateo was named a New York-Penn League Mid-Season All-Star in 2012. The Dominican Republic native has spent the previous 4 seasons transitioning to mostly a reliever role as he continued to rise through the Mets system and in 2016 he spent the majority of the season at the Double-A level where the righty would own a 2.87 ERA in 48 games out of the bullpen. Last season, Mateo split time between the Mets Double-A and Triple-A teams, appearing in 18 games for each club, racking up a combined 52 strikeouts in 54 innings pitched. For his career, Mateo owns a 17-12 record and a 3.07 ERA.