He attended Pinecrest High School in Southern Pines, North Carolina, where he played for the school"s baseball team
Following high school, Maness enrolled at East Carolina University, majoring in accounting. He played college baseball for the East Carolina Pirates. Initially a middle infielder, Maness was converted to a pitcher when one of the team"s starting pitchers went down with an injury.
Before the 2009 season, Maness was named a preseason All-American.
On May 3, 2010, he was named Conference United States of America"s pitcher of the week, and after the season, he was named the conference"s pitcher of the year. The Florida Marlins drafted Maness in the 41st round of the 2010 MLB draft, but he did not sign.
The Saint Louis Cardinals selected Maness in the 11th round of the 2011 MLB draft, and Maness signed with the Cardinals. Professional career
Maness started his professional career with the Batavia Muckdogs of the Class A-Short Season New York–Penn League.
After appearing in the All-Star Game, the Cardinals promoted him to the Palm Beach Cardinals of the Class A-Advanced Florida State League.
He finished the season with the Quad Cities River Bandits of the Class A Midwest League. Maness is noted for his control: in 169 2/3 innings pitched in 2012, he allowed only ten walks. Maness was named to the Texas League postseason All-Star team in 2012.
On November 30, 2012 Maness was named the Cardinals" Minor League Pitcher of the Year.
His efforts on the mound helped Double A Springfield as they were named Minor League Team of the Year by Baseball America. On April 29, 2013, Maness was called up to the major leagues due to the Cardinals" struggling bullpen.
Maness made his MLB debut on May 3. He pitched one inning in his debut, against the Milwaukee Brewers at Miller Park in the eighth inning, giving up no hits, and getting three consecutive groundouts (the third out hit to him) for his debut, following the seventh inning debut of Carlos Martinez who was brought up earlier that day.
On May 15, 2013 he became the first Cardinal rookie pitcher since 1900 with three relief wins in his first five major league appearances.
In 66 games with Saint Louis, Maness went 5-2 with 15 holds, 1 save and a 2.32 European Research Area, striking out 35 in 62 innings. He led the team in European Research Area. Maness pitched 5 effective innings in the Cardinals postseason run, posting an European Research Area of 1.80. Unfortunately, the one earned run he surrendered was a three-run home run to Jonny Gomes in Game 4 of the World Series.
The Cardinals would not lead in a World Series game after this home run, falling in six games.
An arbitration-eligible player prior to the 2016 season, Maness and the Cardinals agreed to a one-year, $1.4 million contract on January 15, 2016.