OAKLAND (TNS) — Royals reliever Jason Adam's fastball came in at 93 mph, right at the letters of A’s third baseman Matt Chapman’s jersey, in the eighth inning of Sunday's 3-2 loss to the A's.

There was no second-guessing what would happen next: Chapman dropped his bat barrel and swatted the pitch 391 feet to left-center field. The result was a leadoff homer that broke a 2-2 deadlock as the Royals limped to the finish line of a seven-game road trip with their sixth loss of this West Coast swing.

Whit Merrifield scored on a wild pitch and Salvador Perez hit a solo homer off Sean Manea in the third inning, but the A's starter allowed minimal damage on six hits.

Since beating these A's eight days ago in Kauffman Stadium, the Royals have gone 1-7. The offense has fallen dormant, outscored 31-17 and batting just .178 (46 for 259). Even in Saturday's win here, they collected just four hits.

Royals starting pitcher Brad Keller, working under a pitch limit that allowed him to throw beyond the fifth inning for the first time since moving into the rotation two weeks ago, fell victim to the Royals' anemic bats Sunday.

After stumbling in a 35-pitch second inning, Keller found a way to command his 96 mph fastball and retire nine of the last 13 batters he faced. When he allowed a walk to A's first baseman Matt Olson in the third and a single to Stephen Piscotty in the fourth, Keller induced a a ground ball for a double play on each occasion.

"Bear down and make pitches where you need to — that’ll always give you confidence," said Keller, who pitched 5 1/3 innings.

He was removed from the game in the sixth inning after he'd thrown 85 pitches and struck out four batters. For a third straight outing, he compiled evidence that the Royals made the right in choosing him to take the injured Eric Skoglund's spot as a starter: Keller has allowed four earned runs on 13 hits in his 12 2/3 innings.

"Threw strikes and did a nice job," manager Ned Yost said. "I was hoping we could score a run or two for him and give him a win."

The Royals had a chance in the eighth inning but were thwarted by a close play. Salvador Perez hit a ground ball up the left side that A's shortstop Marcus Semien dived to his right to stifle. Whit Merrifield, who doubled to lead off the frame and moved to third on Mike Moustakas' groundout, charged home after taking a late break on contact.

Semien made a throw from his knees and got the ball to catcher Jonathan Lucroy in time for an out. Merrifield popped to his feet behind the plate after umpire Bill Welke made the call, hands pressed together as he waited for the Royals to decide whether to challenge the tag.

But Royals replay coordinator Bill Duplissea didn't see enough evidence on replay to risk the challenge in a tied game.

"Billy’s the best in the business. I go on his recommendation," Yost said.

The Royals lost for the eighth time in 10 games this month.

Pick-off gone awry: Reliever Scott Barlow caught a bad break in the seventh inning when he tried to pick off Dustin Fowler at first base. The throw hit Fowler in the back as Moustakas, starting at first for the second game in a row, tried to make the pick. The ball ricocheted toward the visiting bullpen, allowing Fowler to take two bases on the error before Moustakas could fire the ball back into fair territory.

Barlow turned to his slider to retire the next batters on a pop-up and a strikeout before Tim Hill faced left-handed hitter Matt Olson. Hill struck out the A’s first baseman to strand Fowler 90 feet from home plate.

One top draft pick secured: The Royals have agreed to sign their third-round draft pick Kyle Isbel, an outfielder from UNLV, at slot value. The 94th pick was valued at $594,800.

Dealings with first-rounders Brady Singer and Jackson Kowar, who pitched this weekend in the Gainesville Super Regionals for Florida, will be delayed until after the Gators’ postseason run ends. Negotiations with left-hander Kris Bubic, the Royals’ competitive balance pick, won’t progress until he takes the last of his finals at Stanford.

Oklahoma State right-hander Jonathan Heasley, one of the 22 college pitchers selected by the Royals in this year’s draft, announced on his Twitter account Sunday that he signed with the Royals.

“Such a blessing to have the opportunity to start my professional baseball career in the Royals organization,” wrote Heasley, who was selected in the 13th round. “None of this would have been possible without support from family, friends, teammates and coaches. Thank you Oklahoma State for an unforgettable two years. God is good!”

Up next: The Royals, who dropped to 22-44, return home for an eight-game homestand that begins at 7:15 p.m. Tuesday. Royals starting pitcher Ian Kennedy is scheduled to face Sal Romano in the first of two games against the Cincinnati Reds.