That came after Downs was brought in to face pinch-hitter Jonny Gomes and he gave up a two-run homer that pulled the Boston Red Sox to a 5-4 victory on Friday night at Fenway Park.
That climaxed the Red Sox' four-run sixth inning that wiped out a 4-1 Royals lead with a sellout crowd of 37,743 watching the resumption of play after the All-Star break.
Royals right-hander James Shields, a bit rocky at first, had settled down as he took the three-run advantage into the sixth.
That's when Daniel Nava got a one-out single that slipped out of the diving Alex Gordon's glove in left field and Xander Bogaerts belted a two-run homer to center field.
"I was just trying to throw a slider down and away," Shields said. "It was away, but it was up in the zone, kind of in his natural zone. It was one of those pitches I wish I could've had back."
Then, Stephen Drew got a ground-rule double that bounced over the wall after center fielder Lorenzo Cain seemed to be closing in on it.
"We had some unfortunate plays happen. Gordo dove and almost caught that ball. Cain almost caught that ball out in right," Shields said.
Shields struck out David Ross for the second out and that's when Yost pulled his No. 1 starter for Downs, a left-hander. Frankly, he doubted that the Red Sox would use the right-handed Gomes to bat for lefty Jackie Bradley Jr. at that point.
"No. I gambled and lost right there," Yost said. "We get all this information. They pinch-hit one time in the last few [games] in the seventh inning, a bunch in the eighth and the ninth. I wasn't sure they were going to do it in the sixth."
But Red Sox manager John Farrell did make that move and Gomes belted a 2-2 pitch over the center-field wall for a 5-4 lead.
"I just felt like with the matchup of Downs coming in to try to get the two left-handers in Bradley and [Brock] Holt … was a favorable matchup for us," Farrell said. "And Jonny's done it a number of times where he comes off the bench and hits a big home run."
In fact, it was Gomes' sixth pinch-hit homer for the Red Sox, passing Joe Cronin's five. Only Ted Williams, with seven pinch blasts, has more in Red Sox history.
Yost knew well that Gomes was just 3-for-13 against Downs over the years.
"But when you sit back and analyze it after the fact, which is a lot easier to do than before the fact, it was the wrong move," Yost said. "Gomes makes a living off of left-handed pitchers coming in like that and it was just a bad decision on my part on three or four different levels."
"I should have stuck with Shields to get us through that inning. He was at 111 pitches [actually, 112], Bradley was 0-for-2 off him, and I just outsmarted myself."
If Yost was second-guessing himself, Shields declined to participate.
"I didn't think it was a bad move. I mean, that's part of the game. I didn't do my job getting outs there," Shields said.
As for Downs, he didn't second-guess his home-run pitch.
"I went and looked back. I wouldn't have done one thing different," Downs said. "In a long time, that's one of the best times I've thrown the ball. That's baseball taking over. He stayed on a good pitch and hit it. And that's the end."
The Royals got four runs off Red Sox Clay Buchholz, including two in the fourth that broke a 1-1 tie. Omar Infante singled to right and Eric Hosmer followed with a shot that bounced just inside first base and rolled right into the glove of the blonde girl assigned to capture foul balls. Except this one was fair.
As Hosmer took second, Infante's run toward home was halted because the ball was dead due to the interference. Yost questioned plate umpire and crew chief Gary Cederstrom about it.
"His judgment was he wouldn't have scored; my judgment was he would have, but my judgment doesn't count," Yost said.
No matter because Salvador Perez singled Infante home and Gordon did likewise with Hosmer. And in the fifth, Hosmer knocked in Nori Aoki with the Royals' fourth run.
But, in the end, it wasn't enough.
"We had enough runs to win if I'd have managed the pitching right," Yost said.