McWilliams went went 6-2 with a 1.30 ERA with Beech High School in Tennessee and has signed with Tennessee Tech.
The Draft concludes on Saturday, with exclusive coverage of Rounds 11-40 beginning on MLB.com at 1 p.m. ET.
Erik Bacharach is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.