In his senior year, in 2009, he experienced an increase in velocity, reaching 95 miles per hour (153 km/h), which drew attention from scouts.

He finished his senior year with a 6–1 win–loss record, a 0.51 earned run average (ERA) and 79 strikeouts in 41 innings pitched.

[2] With the Virginia Cavaliers baseball team, Kline was used as a relief pitcher in his freshman and sophomore years.

[3] He made his professional debut after signing with the Aberdeen IronBirds of the Class A-Short Season New York–Penn League, where he compiled a 4.50 ERA in 12 innings.

He began the 2014 season with the Frederick Keys of the Class A-Advanced Carolina League, and was named their Opening Day starting pitcher.

On April 20, he was recalled to the major league roster for the first time, as the 26th man for a double-header versus the Minnesota Twins.