HOUSTON -- The formula that propelled the Royals to winning four straight games entering Tuesday night disappeared in the second game of a three-game set against the Astros.

An atypical rough night from the Royals defense led to starter Brady Singer struggling through five innings, and the offense was shut out in the Royals’ 4-0 loss at Minute Maid Park, giving them their second loss in their last nine games.

Six days after holding the Astros scoreless until the seventh inning, when he allowed two runs, Singer faced trouble early and often on Tuesday. The right-hander battled through four walks and seven hits, allowing four runs (one earned) on 104 pitches to get through five innings.

The three unearned runs came in the first inning. First baseman Ryan O’Hearn -- filling in for an injured Carlos Santana (hip flexor strain) -- booted Jose Altuve’s leadoff grounder, which was originally called a hit but later changed to an error.

Then, O’Hearn couldn’t scoop shortstop Nicky Lopez’s throw in the dirt on Aledmys Díaz’s sharp grounder. The official scorer ruled the play as an errant throw that allowed the third run to score.

“You’d like to think when you have an inning like that, you’re going to bounce back and it doesn’t set the tone, but it did,” manager Mike Matheny said. “You could tell in the middle innings that we were having trouble recovering from that.

“But Brady did a great job fighting through a couple plays that we typically make that put us on our heels.”

The defense put the Royals in an early hole that the offense couldn’t overcome. After knocking 13 hits on Monday and averaging more than five runs per game in their last eight games, the Royals were held to just four hits against Astros starter Luis Garcia on Tuesday.

Kansas City had a runner on third base just twice. In the third inning, Michael A. Taylor doubled and then executed a double steal with Jarrod Dyson, who walked. Taylor then tried to steal home against Garcia, who has a long and funky delivery in which he rocks back and forth before throwing the pitch. But Garcia sped up when he saw Taylor take off and threw home in time for catcher Jason Castro to tag Taylor out.

Taylor knew beforehand that Garcia typically takes about four seconds to the plate in his full windup, and Taylor tested him on a previous pitch by taking a big lead off third to see what Garcia would do.

Garcia still went through the full windup. So once Lopez got to two strikes, Taylor thought that was going to be the moment.

“I felt like even if he sped through his windup, if I was able to catch him in between, with two strikes, that I would have a chance,” Taylor said. “And there’s a good chance that he was gripping the breaking ball or offspeed. ... Obviously, there’s risk there, but there are a lot of things that are going to give me a chance.”

Garcia saw Taylor break and only rocked his hands back and forth, rather than his full body. He threw an outside ball to Castro, who was waiting for Taylor at the plate.

“You watch pitchers do it all the time, where it’s a quick pitch once they do go into their windup,” Matheny said. “He goes all the way through that with the side-to-side and whatever else he does. I’m pretty confident Michael’s going to be safe right there. ... If he [was] safe, I think [we’d] all [be] talking about what a momentum shifter that was.”

The Royals tried not to think of what could have been after Lopez singled up the middle with two strikes to lead off the fourth inning, but he was stranded at third base then, too.

Despite the loss and shaky performance by the defense, there were positives to take away from Singer’s outing. He threw eight changeups, a pitch he’s slowly been developing at the Major League level, and saw success with it.

With a runner on second base, two outs and a 1-2 count against a left-handed-hitting Jason Castro in the third inning, Singer threw an outside changeup after throwing two sinkers and a slider. Castro chased it for strike three.

In the fourth, after walking Michael Brantley for the third time, Singer threw two sinkers to lefty Yordan Alvarez for called strikes. He finished Alvarez off with a well-executed changeup in the bottom of the zone for a called strike three.

“I feel like in past outings, you’d see a lot more spiked changeups, lot more cut changeups,” Singer said. “More sporadic with it. I felt like it had good run. … It’s a work in progress. Midseason change, and we’re working on it. It’s not an easy thing to do. I’m enjoying throwing it, learning to throw it in certain situations.”