His first victory came in the third. With Mike Trout on first and Kole Calhoun on second with none out, Albert Pujols dribbled a ground ball to third baseman Danny Valencia. Valencia fired to second baseman Omar Infante for the force at second, then Infante relayed to first to seemingly complete a double play.
But second-base umpire Tim Timmons ruled that Valencia's throw pulled Infante off the bag, moving the runners to second and third with just one out.
Replay officials in New York overturned the call, and Trout and Pujols were both out on the double play.
"The first one ... I couldn't tell. It looked to me like he stayed on the bag, but from where I [was], I couldn't tell," Yost said. "We got on the phone and Billy [replay analyst Duplissea] said 'No, he's out.'"
The overturned call saved the Royals a run, as Josh Hamilton slugged a double in the next at-bat that scored Calhoun to make it 3-0 Angels. Trout likely would have scored had he still been occupying second.
Two innings later, with the Royals nursing a 4-3 lead, another double-play ball prompted a second challenge by the Royals.
After Hank Conger reached on a bunt single with none out, Calhoun rolled a grounder to second for a forceout, but first-base umpire Clint Fagan called Calhoun safe on Alcides Escobar's relay throw to first.
Fagan's call was overturned after a review, as the ball arrived in first baseman Eric Hosmer's glove before Calhoun stepped on the bag.
"Billy Duplissea is right on that stuff, so if the call's not right, I'm going to take every opportunity to challenge it," Yost said.
Jackson Alexander is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.