Whitson attended Chipley High School in Chipley, Florida. As a senior, Whitson pitched to a 0.62 earned run average (ERA) and recorded 123 strikeouts in 55 innings pitched. Baseball America ranked Whitson the third best high school prospect in the United States.[1] He played in the Aflac All-America game and pitched in the Pan American Junior Baseball Championship.[2]
The San Diego Padres selected Whitson in the first round, with the ninth overall selection, of the 2010 Major League Baseball draft. Despite the Padres offering Whitson a signing bonus of $2.1 million, he opted not to sign, surprising the Padres front office.[3][4] Whitson reportedly asked for $2.7 million,[5] but stated that he felt he was not ready for the challenge of minor league baseball.[3]
Whitson enrolled at the University of Florida, and joined the Florida Gators baseball team, pitching in the Southeastern Conference. As a freshman, Whitson pitched to an 8–1 win–loss record, with a 2.40 ERA and 92 strikeouts in 97 innings.[6] He was named a Freshman All-American by Collegiate Baseball Newspaper.[7]
Whitson pitched to a 4–0 with a 3.51 ERA in 2012 as a sophomore. After the 2012 season, he played collegiate summer baseball with the Orleans Firebirds of the Cape Cod Baseball League.[8] He missed the entire 2013 season due to a shoulder injury that required surgery, which was performed by Dr. James Andrews. His labrum and rotator cuff were undamaged.[9][10] The Washington Nationals selected Whitson in the 37th round, with the 1,126th overall selection, in the 2013 MLB draft.[11] Whitson did not sign with the Nationals, returning to college for his senior year. Whitson had a 3.86 ERA with the Gators in 2014, making nine starts and five relief appearances.
The Boston Red Sox selected Whitson in the 11th round of the 2014 MLB draft.[12] He signed on June 20.[13] He pitched for the Lowell Spinners of the Low–A New York–Penn League in 2014.[14]