KANSAS CITY, Mo. — This was Redemption Song Sunday for the Mets bullpen.

Jeurys Familia, showing much better composure and control, pitched the sixth and seventh innings to get the win while Edwin Diaz came on for a clean ninth inning and registered two strikeouts in the Mets’ 11-5 victory over the Royals at Kauffman Stadium.

The Mets will need continued contributions from both relievers if they want to come away with a wild card.

“Familia did a great job, six big outs for us,’’ Mickey Callaway said, “some in a tight game. And then went back out, tough spot to go back out in, probably sat for 20 minutes.’’

After a strong sixth inning, Familia sat for a long time as the Mets put up six runs in the top of the seventh.

“We took him in the cage and had him throw a few,’’ Callaway said of Familia, who got the win to improve to 4-1.

He let up a run in the seventh, but for his two innings of work he threw 30 pitches with 20 strikes.

Familia and Diaz have been working closely with pitching coach Phil Regan on cleaning up their control issues, with Diaz also working to fix his erratic slider.

“That was the best I have ever seen his slider since he has been here,’’ Callaway said of Diaz. “It was 91-92, two to three [mph] harder and it had depth. That was a big outing for him today, a step in the right direction.’’

Diaz, who followed a perfect inning from Brad Brach, told The Post he has been working on his slider grip and is really trying to stay behind the baseball.

“I’ve been spending a lot of time working on my slider and I really feel good about it now,’’ Diaz said.

Familia said his approach now is better from a mental standpoint.

“If I give up a hit or a home run I am trying hard to just get the next batter, not worry what happened in the past,’’ Familia told The Post.

The Mets were trailing 4-3 when Familia came in and he worked a 1-2-3 inning in the sixth. The Mets and Callaway are going to have to trust Familia and Diaz now against the better teams and just such a challenge is coming up with the Indians, Braves and Cubs coming to Citi Field.

Before Sunday, Diaz had allowed seven runs in his last eight outings, so any sign of improvement is a welcome sight for Callaway.