Mayers, 24, was the Cardinals 3rd round draft pick (93rd overall) in 2013 out of the University of Mississippi. He has made 66 career minor appearances, 64 of those starts, posting a 19-24 record with a 3.49 ERA over 350.2 innings pitched and 273 strikeouts.
His 2016 season has been split between Springfield (AA) and Memphis (AAA) with nine starts at each level, posting a combined record of 10-6 with a 2.62 ERA in 106.2 innings pitched.
Mayers will become the first pitcher to make a start for the Cardinals this season who was not a part of the team's starting five from the Opening Day roster. He is the first Cardinals pitcher to make a start in his Major League debut since left-hander Tim Cooney did so against Philadelphia on April 30, 2015 at Busch Stadium.
Socolovich made two relief appearances while in St. Louis, including two scoreless innings last night against the Dodgers, and on July 21 when he tied his career best with three strikeouts against the Padres.
Mayers will wear uniform No. 59.