Brett Anderson, a left-handed pitcher, began his Major League Baseball career with the Oakland Athletics. Drafted by the Arizona Diamondbacks in 2006, he was traded to the Athletics in 2007, where he made his MLB debut in 2009. Anderson quickly established himself as a reliable starter, finishing his rookie season with an 11-11 record and a 4.06 ERA over 175.1 innings pitched. His performance earned him a spot on the Baseball America All-Rookie Team.

Injuries, however, became a recurring theme throughout Anderson's career. In 2010, he was limited to just 19 starts due to elbow issues. The following year, he underwent Tommy John surgery, which sidelined him for the remainder of the 2011 season and most of 2012. Despite these setbacks, Anderson returned to the mound in late 2012, helping the Athletics secure a playoff berth.

The 2013 season saw Anderson transition to a bullpen role after struggling as a starter. He was traded to the Colorado Rockies in December 2013. His time with the Rockies was marred by injuries, including a broken finger and back issues, limiting him to just eight starts in 2014.

Anderson signed with the Los Angeles Dodgers in 2014, where he experienced a resurgence in 2015. He made 31 starts, the most since his rookie season, and posted a 10-9 record with a 3.69 ERA. Unfortunately, injuries struck again in 2016, and he was limited to just four starts.

In 2017, Anderson joined the Chicago Cubs but was released mid-season after struggling with performance and injuries. He then signed with the Toronto Blue Jays, where he finished the season. The following year, Anderson returned to the Athletics, making 17 starts with a 4.48 ERA.

Anderson's career continued with the Milwaukee Brewers, where he signed in 2019. He provided stability to the Brewers' rotation, making 32 starts with a 4.21 ERA. In 2020, the shortened season due to the COVID-19 pandemic saw Anderson make 10 starts with a 4.21 ERA.

In 2021, Anderson re-signed with the Brewers, making 24 appearances with a 4.22 ERA.