Hoover was drafted by the Atlanta Braves in the 10th round of the 2008 Major League Baseball Draft out of Calhoun Community College.[2] He made his professional debut with the rookie ball Danville Braves, posting 4.2 scoreless innings of work. The next year, Hoover split the season between the Single-A Rome Braves and the High-A Myrtle Beach Pelicans, recording a 7–6 record and 3.47 ERA in 26 appearances between the two teams. In 2010, Hoover split the year between the Double-A Mississippi Braves and Myrtle Beach, accumulating a 14–7 record and 3.29 ERA with 152 strikeouts in 153.1 innings pitched. In 2011, he split the season between Mississippi and the Triple-A Gwinnett Braves, logging a 3–6 record and 2.34 ERA with 117 strikeouts in 105.2 innings of work.[6]
He was added to the Braves' 40-man roster on November 16, 2011, a move meant to protect him from the Rule 5 Draft.[7][8]Baseball America ranked him the twelfth-best Braves prospect prior to the 2012 season.[9]
Cincinnati Reds
On April 1, 2012, Hoover was traded to the Cincinnati Reds for Juan Francisco.[10] Hoover started the 2012 season with the Triple A Louisville Bats. On April 24, Hoover was called to the major leagues for the first time.[11] He made his debut the next day against the San Francisco Giants, and retired the side.[12][13] He earned his first career Major League save on September 12, 2012, against the Pittsburgh Pirates.[14] Hoover ended the season with 26 appearances and a 2.05 ERA.[15] He was placed on the Reds' Opening Day roster in 2013.[16] During the 2013 season, Hoover set a team record for right-handed pitchers at 26+1⁄3 innings pitched without an earned run.[17] That year, he pitched in 69 games, and had a 2.86 ERA.[15] Hoover opened the 2014 season with the Reds,[18] and was optioned back to the AAA Louisville Bats on August 21, 2014.[19] At the time, he was 1–10 with a 5.27 ERA in 46 appearances that season.[20] Hoover was recalled to the majors in September and finished the season with a 4.88 ERA.[15] Hoover made the Reds Opening Day roster in 2015,[21] and finished the season with an 8–2 record and 2.94 ERA.[1] Eligible for arbitration for the first time in the 2015–16 offseason, he was awarded $1.4 million.[22] Hoover became the first player to take the Reds to a hearing since Chris Reitsma in 2004.[23] Shortly after spring training began in February 2016, manager Bryan Price named Hoover the Reds closer.[24] On June 28, Hoover gave up his 6th career grand slam, the most in Cincinnati Reds history. He was outrighted off the Reds roster on August 4, 2016, after struggling to a 13.50 ERA in 18 appearances.[25] On October 12, 2016, he elected free agency.
Arizona Diamondbacks
On January 10, 2017, Hoover signed a minor league contract with the Arizona Diamondbacks that included an invitation to spring training.[26] After a strong spring, Hoover won a bullpen job for the D'Backs.[27] In 52 appearances with Arizona in 2017, Hoover posted a 3–1 record and 3.92 ERA with 54 strikeouts in 41.1 innings of work. He was non-tendered by Arizona on December 1, 2017, and became a free agent.
Milwaukee Brewers
On January 10, 2018, Hoover signed a minor league deal with the Milwaukee Brewers organization.[28] He was assigned to the Triple-A Colorado Springs Sky Sox to begin the 2018 season. He had his contract purchased to the active roster on April 7, 2018.[29] He was designated for assignment on April 11 after posting a 20.25 ERA in 2 appearances.[30] He was outrighted to Triple-A on April 15, and elected free agency a day later.[31]
Washington Nationals
On February 1, 2019, Hoover signed a minor league contract with the Washington Nationals organization.[32] He spent the season with the Triple-A Fresno Grizzlies, logging a 6–6 record and 8.47 ERA in 30 appearances with the team. Hoover elected free agency following the season on November 4.[33]
Canberra Cavalry
On November 6, 2019, Hoover signed with the Canberra Cavalry of the Australian Baseball League. In 9 appearances with Canberra, Hoover pitched to a 4–2 record and 3.81 ERA with 51 strikeouts in 52.0 innings of work.
In 2022, Hoover started 11 games for Lexington, struggling to a 2–6 record and 6.34 ERA with 50 strikeouts across 61 innings of work.[36] He became a free agent following the season.