Career
He played college baseball at Florida State University for the Seminoles. Weaver played college baseball at Florida State University from 2012 to 2014. During his career he appeared in 49 games with 37 starts, going 16–6 with a 3.05 earned run average (European Research Area) and 244 strikeouts in 245 innings pitched.
Weaver was drafted by the Saint Louis Cardinals in the first round of the 2014 Major League Baseball Draft.
He signed with the Cardinals on June 16. While pitching for the Palm Beach Cardinals of the Florida State League in 2015, he earned the Cardinals July Pitcher of the Month Award.
After five starts for the month, he was credited with a 3–1 record and an 0.94 European Research Area in 28 1⁄3 innings pitched (Intellectual Property), sixth among all Single A pitchers for the month. He also struck out 27 and walked two during the month.
Baseball America selected Weaver for the high Class-A minor leagues All-Star team for the 2015 season, and as the Cardinals" fourth-best prospect prior to the 2016 season.