KANSAS CITY -- The Royals bullpen entered Wednesday night having allowed one run or fewer in each of the previous 12 games dating back to July 6, a stretch in which the unit led the American League with a 1.39 ERA while pitching the fewest innings among AL bullpens.

They nearly added another game to that trend Wednesday until James McArthur allowed five runs in the ninth inning, blowing his fifth save of the season in the Royals’ 8-6 series-deciding loss to the D-backs at Kauffman Stadium.

The Royals bullpen protected a one-run lead for most of Wednesday’s game after starter Michael Wacha allowed three runs over 4 2/3 innings. All the damage against Wacha came on solo homers, including back-to-back long balls in the fourth inning.

But the Royals responded immediately in the bottom of the frame with three runs, and the score remained 4-3 as McArthur jogged to the mound in the ninth.

Lourdes Gurriel Jr. legged out a one-out single that shortstop Bobby Witt Jr. got a glove on but wasn’t able to make the throw because his legs slipped on the grass.

McArthur then walked Geraldo Perdomo, with ball four coming on a pitch that looked like it nicked the zone. Catcher Salvador Perez was on his way to throwing out Gurriel trying to steal second when the pitch was called a ball.

“I thought it was a close pitch,” McArthur said. “At the end of the day, I can’t control what the umpires call balls and strikes. So for me, I just have to be better not being in a three-ball count to walk a guy. Walks are unacceptable in games like that. I need to do a better job getting ahead in that count.”

Gurriel and Perdomo came around to score on Gabriel Moreno’s go-ahead double. The D-backs hit McArthur hard, culminating in Ketel Marte’s three-run homer -- his third blast of the series.

“That’s a super frustrating inning,” McArthur said. “I felt like I was pretty close at times to getting out of it and just didn’t quite get the pitch I needed to. Some really good defensive plays behind me, balls finding some holes, but at the end of the day, just didn’t execute enough pitches.”

McArthur’s ERA has ballooned to 4.91 this season as the Royals’ closer. The Trade Deadline is just six days away, and the Royals have not been shy about their desire to add at least one more reliever and a bat to help lengthen the lineup. Their pro scouts were in town all weekend in meetings about potential acquisitions, and the Royals want to be aggressive when it comes to upgrading their team by 5 p.m. CT next Tuesday.

The hierarchy of the bullpen has already shifted with Hunter Harvey’s acquisition, and Wednesday’s blown save illuminated the need for even just one more move. For example, Harvey pitched the eighth inning Wednesday, working his way out of a jam when he had runners on the corners and one out. His availability gives manager Matt Quatraro another option in high-leverage situations, allowing relievers like John Schreiber and Chris Stratton to pitch in lower-leverage and work out their recent struggles.

Another acquisition like Harvey could do the same with McArthur, whom the Royals still believe can pitch big innings for them down the stretch.

“The ninth inning is not an easy inning to come in and get three outs,” second baseman Michael Massey said. “There’s a reason there’s only 30 of those guys. [McArthur] will bounce back. He’s been good for us all year, and this is just part of it.”

Despite the frustrating loss Wednesday, the Royals have won four of six games coming out of the All-Star break. They still have three more games on this homestand and will take their 35-20 record at The K into this weekend’s series against the Cubs after Thursday’s off-day.

The Royals began the unofficial second half two games behind the Red Sox for the third AL Wild Card spot; now Kansas City is a game up on Boston and a game behind Minnesota for both the second AL Wild Card spot and second place in the AL Central.

“We’re in a good spot,” Massey said. “Tonight’s frustrating. But it’s baseball. I’m sure we’re going to steal a save from somebody else and come from behind and win a game in the ninth, too. So just kind of the way it goes. … We’re going to be in this thing the whole way.”