Aaron Loup, a left-handed pitcher, began his Major League Baseball career with the Toronto Blue Jays. Drafted by the Blue Jays in the ninth round of the 2009 MLB Draft, Loup made his debut on July 14, 2012. Known for his sidearm delivery, he quickly became a reliable option out of the bullpen for Toronto.

During his rookie season in 2012, Loup appeared in 33 games, posting an impressive 2.64 ERA. His ability to effectively handle left-handed hitters made him a valuable asset in the Blue Jays' bullpen. In 2013, he continued to build on his initial success, pitching in 64 games with a 2.47 ERA and earning his first career save. Loup's consistency on the mound was evident as he maintained a low walk rate and demonstrated excellent control.

Loup's tenure with the Blue Jays lasted until 2018. Over these years, he remained a steady presence in their bullpen, appearing in over 300 games. His performance in the 2015 season was particularly noteworthy, as he helped the Blue Jays reach the postseason for the first time in over two decades. Although his ERA rose to 4.46 that year, he played a crucial role in the team's bullpen depth.

In 2018, Loup was traded to the Philadelphia Phillies, where he finished the season. His time with the Phillies was brief, as he became a free agent at the end of the year. In 2019, Loup signed with the San Diego Padres, but his season was cut short due to an elbow injury that limited him to just four appearances.

Loup's career saw a resurgence in 2020 when he joined the Tampa Bay Rays. In the pandemic-shortened season, he pitched in 24 games, recording a 2.52 ERA. His performance helped the Rays secure a spot in the World Series, where they ultimately fell to the Los Angeles Dodgers. Loup's ability to neutralize left-handed hitters was a key component of the Rays' bullpen strategy.

The following year, Loup signed with the New York Mets. In 2021, he delivered one of the best seasons of his career, achieving a remarkable 0.95 ERA over 65 appearances. His exceptional performance was characterized by his ability to keep hitters off balance and limit hard contact. Loup's success with the Mets solidified his reputation as a dependable reliever.