KANSAS CITY -- When you’re looking up at a cluster of teams that are vying for an American League Wild Card spot, the margin for error isn’t large.

For the Red Sox, that margin for error got just a little smaller on Saturday night as Boston fell to the Royals, 5-4, on Nick Pratto’s solo homer off Garrett Whitlock with two outs in the ninth at Kauffman Stadium.

Whitlock had come on in the seventh and looked excellent while retiring the first eight batters that he faced. But just when it looked like the Red Sox were headed for extra innings, Pratto slammed a 3-2 pitch over the center-field wall to send the Royals prancing and dancing toward home plate to greet the rookie first baseman.

“I threw a 3-2 changeup,” Whitlock said. “It was a mistake and he hit it out. I’m [upset], not at you all [the media], but at myself. The guy made a good swing, but that was a terrible pitch by me.”

The sudden ending capped a frustrating night for Boston, which has dropped two of three in this four-game set. The Red Sox came from behind twice to tie the game at 3-3 and 4-4, before Pratto’s heroics ended it.

Starter Nathan Eovaldi struggled early, but the right-hander got stronger as his outing went on. The Red Sox trailed, 3-1, when Bobby Dalbec provided an interesting development with a two-run homer to right-center in the fourth. There were questions in recent days about how many opportunities Dalbec will get now that Eric Hosmer has come on board after a Trade Deadline deal with San Diego.

Hosmer started the opening two games of the series at first base, but Dalbec got the call on Saturday with Royals left-hander Daniel Lynch on the mound. Dalbec responded with three RBIs.

“We’ll maximize our bench,” manager Alex Cora said. “That was a good swing [by Dalbec]. A pitch in the zone and he drives it to right-center.”

Another homer by Alex Verdugo in the sixth erased a 4-3 Kansas City lead. But Boston’s offense shut down from that point on.

“We put together some good at-bats, but the last third of the game we expanded,” Cora said. “Good effort, but we didn’t finish the game.”

Eovaldi wound up grinding through six innings, allowing seven hits, four runs and no walks to go with seven strikeouts.

“We need to win all these games right now,” Eovaldi said. “I’ve got to set the tone. I’ve got to come out from the first pitch ready to go.”

The Red Sox, who took two of three in Houston before moving on to Kansas City, can still salvage a winning road trip if they can prevail in the series finale on Sunday.

“You tip your cap,” Cora said, “and move forward.”