“Kind of a strange day,” Neil Walker said Saturday night, after the Yankees barely avoided getting swept by the Royals at their home, securing the nightcap with a 5-4 victory after dropping the opener, 10-5.

Strange for sure, including Walker making his big-league outfield debut, new guy Zach Britton earning both boos and a Bronx cheer and Shane Robinson tallying his first pinstriped homer — and Chasen Shreve saying his goodbyes at the conclusion as he departed for the Cardinals in a trade.

There’s strange and then there’s concerning, and little doubt exists where you file Luis Severino’s continuing struggles in Game 1.

The Yankees might be able to retain their playoff spot with a shaky Severino. Yet to win it all without an ace-quality Severino would be extremely challenging.

The right-hander lasted just 4 ²/₃ innings, allowing six runs, including former Met Lucas Duda’s homer, on eight hits and a walk as he walked five. Severino, who compiled a 1.98 ERA in his first 18 starts now has an 8.84 ERA in his past four starts thanks to 19 runs allowed (and seven homers) in 19 ¹/₃ innings.

“I don’t know what is the issue, but I will make sure I will recover,” Severino said. “I’ve been through this in the past, so we know I just need to work on the stuff that’s not working and try to be myself again.”

That begs the follow-up query: What’s not working? According to Severino, Boone and Saturday’s catcher, Austin Romine, command ranks as the top problem. Severino’s 95th and final pitch of the day, a belt-high fastball, took a ride over the right-field wall courtesy of former Met Lucas Duda, whose two-run homer put the Royals up by a 6-0 count. In Severino’s previous start July 23 against the Rays at Tropicana Field, Boone said, a misplaced slider led to seven runs, six earned, and two homers in five-plus innings.

“That’s something that we get into the video and probably [pitching coach Larry Rothschild], who’s as good as there is finding little things, maybe it’s one small thing that gets him back on track,” Boone said. “But we’ll have to dive back into that.”

The Yankees are now 8-8 in their past 16 games, their worst such stretch since they started the season by winning half of their opening 16, and the record not being worse in that stretch serves as a tribute to Severino’s rotation mates picking up for their ace.

Sonny Gray has won three straight starts, and Masahiro Tanaka shut out the Rays this past week at the Trop. Luis Cessa pitched respectably. CC Sabathia, making his first start of the second half on Saturday night, kept the Yankees in Game 2, even if he lasted just 4²/₃ innings. And Happ joined the team on Saturday, primed to make his pinstriped debut Sunday against the Royals then take on the Red Sox next weekend at Fenway Park.

Severino’s next turn, good health permitting, also will be at Fenway, so some urgency exists for the 24-year-old to diagnose and fix the problem. Let’s face it, though: The Sawx play as heavy favorites to hold onto the AL East, and the Yankees in turn own strong odds to qualify for the postseason as a wild-card entry.

And that’s when Severino can really make the difference. The Astros displayed just last fall, with Justin Verlander, the immense value of an ace pitching like an ace in October. Perhaps Tanaka can do that again, as he did last year. Severino, however, stands as the better bet to reassume that role.

Asked if he feels pressure as the team’s ace, Severino said, “I don’t. I just need to, like last year, go to the mound and do a good job. Right now, I’m not doing a good job. I need to get better. That’s the bottom line.”

The bottom line, too, is Severino likely will go forward without an imported co-ace like Jacob deGrom or Madison Bumgarner. Once Tuesday passes without a high-end upgrade, he’ll officially become the most important man on this Yankees roster. There’s nothing strange about that.