KANSAS CITY -- As the Royals push forward in their rebuild, they know the one area that has to improve is their bullpen.

Kansas City’s ‘pen came into Wednesday night’s series finale against the Braves sporting the second-worst ERA (5.04) in the American League to Baltimore’s 5.68. And Royals relievers were front and center of a 10-2 loss to the Braves at Kauffman Stadium.

• Box score

In his final start of 2019, Royals left-hander Mike Montgomery labored, but he limited the damage. He gave up two runs over 4 2/3 innings -- both coming with two outs in the fifth.

After getting two quick outs in the fifth, Montgomery walked Ozzie Albies after getting ahead of him 0-2. Josh Donaldson then belted an RBI double to left-center. Nick Markakis followed with an RBI single to center, tying the score.

But right-hander Jacob Barnes, who got the final out of the fifth inning, gave up a single and two walks to load the bases in the sixth. One of the walks came to light-hitting Billy Hamilton. Right-hander Heath Fillmyer came on and gave up a two-run single to Dansby Swanson and a sacrifice fly to Albies, and the rout was on.

Barnes’ ERA ballooned to 7.39.

“The walk to Hamilton,” Barnes said, “that's just the one that's frustrating because that's a guy I should attack. I just kind of missed outside a couple times. That was the frustrating one for sure. Obviously, I put Filly in a tight spot when he came in. That was frustrating, walking Hamilton right there."

After Tim Hill pitched a scoreless seventh, right-hander Jesse Hahn gave up two hits, two walks and four runs in the eighth in one-third of an inning. Hahn, who is trying to come back from elbow repair surgery, now has a 13.50 ERA in his six outings.

“Obviously, it’s a little frustrating,” Hahn said. “I hate saying this, but it is like Spring Training for me. I have five or six innings under my belt. I’m still dealing with timing, mechanics, rhythm. And sometimes I’m fighting myself. When you do that and walk the leadoff guy, it just gets out of hand.

“I do feel like my stuff gets better with every outing. Even though my command wasn’t great today I still have feel for my pitches a little bit better every outing. I’ll get more comfortable. My arm feels great. It’s just about going out there and competing.”

Kyle Zimmer, also making a comeback from several injuries, gave up a run in the ninth -- his ERA is 11.42.

Royals manager Ned Yost, who has said often that the team’s pitching simply has to improve for them to compete again, maintains the talent is there.

“Our pitching needs to improve in terms of pitch execution,” Yost said. “We make a lot of mistakes. We struggle to command down and away. Look, saying this is really easy. Doing this is really hard. It takes a lot of work to be able to do it. You have to be able to suppress offense, suppress power, by execution on pitches down and away. … We just make way too many mistakes."

And many of those mistakes come from Royals middle relievers, as they did against the Braves, turning a 2-2 game in the sixth into a rout.

"It doesn't matter where they come,” Yost said. “They come. Nobody is going to be perfect, but you look at the elite pitchers in this league and they're elite for a reason, because they've got great stuff, but they can command. That's going to be something they're going to have to focus on going forward.”