In the bottom of the sixth inning, reliever Jacob Waguespack entered the field to relieve starter Nate Pearson, but once he got to he mound he was directed to the dugout by home plate umpire Alan Porter. Moments later, Rafael Dolis began his warmup pitches to come into the game.
Sportsnet’s Hazel Mae reported that the official ruling was that Waguespack was deemed ineligible to enter the game as he did not appear on the official lineup card that Porter was given. Waguespack was optioned early Thursday only to be recalled prior to the game when the Blue Jays placed Trent Thornton on the injured list.
It is speculated that manager Charlie Montoyo failed to update his lineup card to reflect the pre-game roster transaction.
However, rule 4.03(c) of Major League Baseball’s Official Baseball Rules mention that the listing of relievers—and other substitute players—is only a “courtesy” and that “the failure to list a potential substitute player shall not make such potential substitute player ineligible to enter the game.”
If my reading of the rules is correct, then if Waguespack was officially recalled, then he should have been eligible to pitch the game even if he wasn’t listed on the lineup card. In that case, Montoyo could have presented the rule to the umpiring crew to appeal and, if necessary, play the remainder of the game under protest.