It was the thought of his team's mental errors on display again that draw Porter's ire.
The Royals were the first team to pounce on Astros starter Scott Feldman this season, knocking nine hits off the Houston ace and rolling to a 5-1 win Thursday night to complete a three-game sweep in Minute Maid Park.
Though the Astros have scuffled out of the gate so far this season, they had avoided the all-too familiar sweeps of last season's 111-loss campaign.
The Royals reacquainted them with the brooms.
It came in sloppy fashion for the Astros, especially after a fifth inning baserunning gaffe from Matt Dominguez, as the third baseman tried to stretch a shallow no-out gapper into a double with a runner already on.
"It's just not smart, obviously," Porter said. "I went and asked Matt Dominguez and said, 'Do you think you're invisible?' You're down, 5-0, and the ball is right in front of you. No, I don't like that play."
By the time that chance came around, though, the Astros were already facing an uphill battle. Feldman had surrendered seven hits combined in his first three starts and entered Thursday's contest with a league-best 0.48 ERA.
But his night got off to a dubious start thanks to another mental error, this one also counted as an error in the box score.
A first-inning fielding miscue by newly-minted Major Leaguer George Springer allowed Nori Aoki to reach third, eventually leading to an unearned run.
"That's a double all the way," Porter said. "You're talking about a speed guy who hit a ball past a diving first baseman. There's nothing you can do to stop him from getting to second base. Just secure the ball and hit the cutoff man.
"That there is more of a mental error than it is a physical error."
But the hit itself highlighted how relentless the Royals were from the outset, never easing Feldman back into the flow of the game after he missed four days on the bereavement list following the death of his father.
"It seemed like they put the bat on the ball early and often," Feldman said. "It was tough to get some swing and misses. They found a lot of holes. Just one of those nights right from the get-go."
The Royals would score in three of the next four innings, including a two-run fourth built around Alcides Escobar's two-out, two-RBI double.
Feldman still managed to last six innings, while allowing a season-high five runs -- four earned -- and recording just two strikeouts. He's still the first Astros starter to complete six or more innings in his first four starts since Brett Myers did it six times to open the 2011 campaign.
"Out of the first four games, my arm and stuff actually felt the best tonight," he said. "Sometimes, your luck can run out. "
Meanwhile, Royals starter James Shields needed no luck against the home team. The righty struck out 12 Houston hitters over eight innings to stymie the struggling Astros.
"He was good, throwing his cutter and changeup for strikes," Dominguez said of Shields. "He had three or four pitches working tonight. Whenever he's got those going, he's pretty tough."
The 12 strikeouts were Shields's highest total as a Royal and the most for any Kansas City pitcher since Zach Greinke struck out a dozen against the Reds in June 2010.
Shields said it was as simple as letting the struggling Houston offense swing the bats.
"That's an aggressive team over there," he said. "When you get ahead in the count and make your pitches, you're successful. It worked tonight."
Despite the touted Springer's recent call-up, the Astros' lineup remains mired in a season-long slump and it finally cost them a sweep, one in which they scored seven runs in 29 innings.
Twelve players have at least 20 at-bats for Houston so far this season. Only four -- Jose Altuve, Jason Castro, Jesus Guzman and Dominguez -- are batting above the .200 mark. It was the 11th time in 16 games that the Astros haven't been able to score at least three runs. They are now 1-10 in such games.
The Astros pushed across their only run in the fifth inning, when Alex Presley's sacrifice fly plated Chris Carter after Dominguez's baserunning mistake shortened a potential big inning before it could begin.
"It's just bad baseball," Dominguez said. "Down by five, that's a poor decision and I realize it. I wish I could take it back, but that stuff can't happen if you want to win games."
Reliever Anthony Bass salvaged a sliver of silver lining from the defeat, tossing three perfect innings to keep the Astros' bullpen fresh after Wednesday's extra-inning loss.
"He pretty much saved the rest of the bullpen," Porter said. "A lot of times, that goes unnoticed, but if he hadn't handled things, it puts us in a tough situation going into Oakland. He also gave our offense a chance."
One the Astros couldn't seize, which is an increasingly common occurrence against Kansas City.
The Royals have now swept consecutive three-game sets against the Astros, dating back to last season, and have won seven of their last eight against Houston.
A quick turnaround awaits the Astros, who begin a six-game West Coast road trip Friday against the A's.