KANSAS CITY, Mo. — Mets pitching coach Phil Regan held his left thumb about a half-inch from his index finger on Saturday when discussing his pet project.

“I think we’re this close,” Regan said, referring to Edwin Diaz and a possible resurgence for the beleaguered reliever.

Diaz had entered in the eighth inning with the bases loaded a night earlier against the Royals and walked the first batter he faced before surrendering an RBI single. A subsequent grand slam by Ryan O’Hearn was overturned on replay, but two of the runners Diaz had inherited from Brad Brach already had scored, turning the Mets’ 2-1 deficit into a three-run hole.

The right-hander entered Saturday 1-6 with a 5.44 ERA as he looks to regain closer’s form. For now, Seth Lugo has assumed the closer’s role as the Mets try to get Diaz right.

“I have been working really hard,” Diaz said. “I have been getting to the ballpark earlier to try to work on different things and I think the last two outings that I have had, I’ve had some better results.”

Diaz was asked if team officials had suggested a minor league stint to work out his troubles.

“They haven’t mentioned anything to me,” Diaz said. “In contrast, they have actually told me they are looking to count on me in big situations.”

The biggest key is Diaz’s slider, which has abandoned him for a large portion of this season. Without that pitch as a weapon, right-handers are batting .321 against him. Diaz recently has been reporting to the ballpark at 12:30 p.m. for night games to put in extra work on the pitch with Regan.

“We’re working on a few things trying to get his slider back,” Regan said. “That’s the main thing we want to get back, and a quality slider. His fastball is pretty good right now and his direction is pretty good. I don’t know if they are sitting on [the fastball], because he’s still throwing his slider, but they are not the quality sliders we want him to have. But I think we’re close.”

It’s certainly been a different Diaz than general manager Brodie Van Wagenen thought he was acquiring last offseason, when he parted with top prospects Jarred Kelenic and Justin Dunn to get Diaz and Robinson Cano from the Mariners. That Diaz had pitched to a 1.96 ERA with 57 saves last season.

“Mentally, I am 100 percent fine,” Diaz said. “I am positive all the time, so it’s just the mechanics I have to tweak a little bit.”

Though a bases-loaded jam in a tight game in the eighth inning might not have been an ideal spot for a pitcher trying to regain confidence, Diaz told Regan he’s glad he received the opportunity.

“A lot of people said, ‘Why put him in that situation [Friday] night?’ ” Regan said. “And [Diaz] said to me today: ‘That gave me confidence, because I haven’t been in that situation in a while and I loved it. It picked me up.’ He’s in a great state of mind right now.”

And with six weeks remaining and the Mets still in the postseason hunt, Diaz anticipates he can still rewrite his season.

“I see myself as a pretty important part,” Diaz said. “When I first came here I came to win and it hasn’t changed for me. The season hasn’t gone as I have really wanted to or the team has wanted to, but I think going forward we can make a lot of good games.”