The team also announced that McGuire, 23, will make his major-league debut behind the plate against the Cleveland Indians. He was originally acquired by the Blue Jays back in 2016 in the deal that sent Drew Hutchinson to the Pittsburgh Pirates for Francisco Liriano and McGuire.
In 96 games with triple-A Buffalo, McGuire finished with seven home runs, 37 RBIs and a .233/.312/.339 batting line.
Shafer, 25, has appeared in three games for the Blue Jays allowing a hit and three walks while striking out two in five innings of work. In 34 games with triple-A Buffalo, the Shafer is 3-3 with a 1.41 ERA and 32 strikeouts over 38.1 innings.