HOUSTON -- The Royals kept opposing hitters on their toes for most of Monday afternoon’s game at Minute Maid Park. When it mattered most, though, the Astros showed how dangerous they are.

Kansas City blew a five-run lead and suffered a 7-6 walk-off loss at the hands of Yordan Alvarez, whose 444-foot homer in the bottom of the ninth against Scott Barlow gave Houston all the fireworks it needed on the Fourth of July.

The loss put a damper on starter Jonathan Heasley’s quality start, wasted MJ Melendez’s first career multihomer game and made this four-game series all the more daunting with the Royals set to face right-handers Luis Garcia (3.54 ERA), Cristian Javier (2.58 ERA) and Justin Verlander (2.03 ERA) over the next three games.

“That’s one of the tougher [losses] this season,” manager Mike Matheny said. “… Thought [Heasley] threw as good as we’ve seen him throw. Like the chances of us being able to finish that off.”

The Royals’ front office explained its offseason plans last November, emphasizing the need for a strong bullpen. They needed back-end relievers to complement Barlow and Josh Staumont and help close games, especially when their young starters -- who are all still learning quickly on the job -- give them good outings.

Heasley didn’t allow a hit until the fourth inning and allowed two runs (one earned) in six innings for his fourth quality start of the season. He worked out of jams in the fourth and fifth before shutting down the middle of the Astros’ lineup in the sixth. In his last start against the Rangers, Heasley allowed seven runs in 3 2/3 innings. He threw just three sliders and afterward admitted he likely should have thrown more, although his issues stemmed from a lack of command on all of his pitches. 

On Monday, Heasley threw everything he had at Houston's lineup to keep it as off-balance as he could: 38 fastballs, 19 curveballs, 18 sliders and 17 changeups. 

“That was a big part of the game plan, especially with my spin pitches,” Heasley said. “I didn’t really establish those last outing, and that was the game plan from the get-go. We’re going to establish those, get the curveball going, get the slider going a little more. Try to get these guys off-balance. Because if I stay heavy fastball, they’re going to hit it. And when I threw the fastball today, I felt like I had pretty good command of it and executed it well.”

The offense pounced on Astros starter Jake Odorizzi for five runs in the first three innings, so Heasley worked with a lead and exited after the sixth with the Royals up three runs. 

“It’s the kind of start he’s going to win more often than not,” Matheny said. “Gave us a chance. Put us in a position to do so.” 

After the Astros scored a run against right-hander Wyatt Mills in the seventh and Jeremy Peña led off the eighth with a walk, Matheny turned to lefty Amir Garrett to face the middle of Houston's lineup -- two left-handed hitters in Alvarez and Kyle Tucker with Alex Bregman in between. 

That spot is why the Royals acquired Garrett in Spring Training.

Garrett has had his ups and downs this year, struggling with command, but he entered Monday holding lefties to just a .067 average (2-for-30), while righties have a .231 average (9-for-39) against him. Six of Garrett’s past seven appearances before Monday had been scoreless. 

“We know when he’s in the zone, he gets outs,” Matheny said. “Right there, he’s got a tough assignment. Two really good lefties. We need him to do what he does -- get them out and hand the ball over to Scott in the ninth.” 

Garrett walked Alvarez and Bregman to load the bases, then he allowed a two-run single to Tucker.

“I think I’m nitpicking a little bit,” Garrett said. “In the past, I’ve never done that. … I’m thinking about it too much. In the past, when I’ve been awesome, it’s like, ‘I’m going to go up there and it’s going to be me versus you.’ I think ... I’m battling myself right now.”

Taylor Clarke surrendered a game-tying RBI single to Yuli Gurriel but got the Royals out of the inning with the game knotted at 6, and Barlow was one out away from forcing extra innings when he hung a slider to Alvarez.  

The three-run eighth loomed large, especially after assessing Heasley’s outing. 

“Hopefully, we turn it around here. These guys deserve it,” Garrett said. “A ballgame like this, we deserve to win it. I didn’t do my job today. I lost it for us. I can take that. I’ll put it on my shoulders. It was my fault.”