The A's rallied for four runs off Junis and reliever Buch Smith in the fateful eighth inning.
The inning started when Junis threw a changeup down and in that Dustin Fowler blooped into no-man's land in center field.
"One of the few changeups I do throw," Junis said. "It was a good pitch and he blooped it off the end of the bat. Just didn't fall my way there."
One out later, Fowler stole second when catcher Salvador Perez whiffed on catching a 1-0 changeup to Jed Lowrie.
Junis then fell behind 3-0 to Lowrie, though each appeared to nick the outside corner. Junis then threw a sinker that caught too much of the plate and Lowrie lined an RBI single to center, giving the A's the lead.
"We had guys going everywhere down there [in the bullpen]," Yost said. "We had Timmy Hill up for [A's first baseman] Matt Olson, we had Burch Smith up if we gave up the lead. My mindset was that Khris Davis was going to be Jake's last hitter and then Timmy for Olson, whatever we could do to get to Kelvin [Herrera] in the ninth with the score tied.
"I wasn't going to use Mac down one and not have him for tomorrow."
Smith walked the first hitter he faced, and fell behind 3-0 to Olson, who then got the green light and belted a three-run home run. The home run was estimated to have traveled 454 feet, per Statcast™.
MOMENT THAT MATTERED Junis' slider was effective all day, and he used it when he needed it in the fifth inning. With two outs, Dustin Fowler singled sharply up the middle. Then Marcus Semien drew a walk. But Junis silenced the threat when he got Jed Lowrie swinging on a 1-2 slider down and in.
SOUND SMART Jay's home run was his first since July 5 of last season when he was with the Cubs, and it was over a span of 442 at-bats, which had been the longest active homerless span for a non-pitcher in MLB.
HE SAID IT "Not to give away one of our secrets, but when the "Get Loud!" sign comes on the scoreboard and the crowd gets loud, the pitcher can't hear. It's a good time to take off." -- Royals' Whit Merrifield, on how he stole third base in the sixth inning
UP NEXT Left-hander Danny Duffy (2-6, 5.71 ERA) takes the mound for the Royals as they open a three-game set in Anaheim, Calif., against the Angels on Monday at 7:07 p.m. CT. Duffy has put together two straight strong outings, the latest against the Twins in which he gave up just four hits and one run over six innings. Right-hander Nick Tropeano (3-3, 3.80 ERA) will pitch for the Angels.