Yankees designated hitter Anthony Rizzo hits a three-run home run...

Yankees designated hitter Anthony Rizzo hits a three-run home run against the Mariners during the first inning of an MLB game at Yankee Stadium on Aug. 1. Credit: Kathleen Malone-Van Dyke

ST. LOUIS — Anthony Rizzo didn’t start for a second straight game Saturday night with the lower-back tightness that caused him to be a last-minute scratch Friday night.

And while Aaron Boone said late Saturday afternoon that the first baseman was “better,” he copped to not knowing exactly what that means long-term.

“Obviously not in the lineup,” Boone said about three hours before his team’s 1-0 loss to the Cardinals. “I was actually just talking to him, and it doesn’t feel like last time [early July] when he missed four [games] . . . not saying he won’t [this time], but he doesn’t feel like that. He was better today, but we’ll see where we’re at at the end of today and into tomorrow.”

What happened Friday that led to the late scratch? “It just kind of gradually . . . It was fine all day, fine warming up, fine hitting, so it just kind of grabbed really oddly,’’ Rizzo said. “It didn’t really even grab that much, but then when I came in to cool down and was stretching and working it, that’s when it started spasming a little bit. So just wanted to be smart and not make it something where it’s an extended period of time.”

Is Sunday a possibility? “I think it’s still that part of the year to be smart, so realistically probably not,’’ Rizzo said. “But if I wake up and feel really good, that’s kind of how this thing goes, so we’ll see . . . Feels a lot better than yesterday, so we’ll see.”

Is Rizzo concerned that this is the second time this has happened in a month? “Whenever it happens, there’s always concern,’’ he said. “It’s frustrating not playing.”

Rizzo is hitting .227 but has 27 homers and an .858 OPS.

“I’ve dealt with this in years past, and I just feel like we’ve been ahead of it big time,” he said on July 8. “I went on the IL for it once . . . That was in April [of 2018] to be super-cautious just because it was April. Back pain is the worst, but the progress we’ve made with the treatment is great.”

“He’s dealt with back issues throughout his career,” Boone said. “It’s something he’s proactive with and with his warmup and things. It’s all part of his process of making sure he does a lot of maintenance work so that these things don’t pop up that much. We’re mindful of it.”

Odd circumstances

Righthander Frankie Montas, the Yankees’ headline acquisition at the trade deadline, still is slated to start Sunday afternoon’s series finale even though he hadn’t arrived in St. Louis as of late Saturday afternoon (Boone said he was due to arrive at some point late Saturday afternoon or early evening). Montas, who has yet to meet his new team in person, was placed on the bereavement list Wednesday after the death of his mother-in-law.

“Everything’s in line to pitch,” Boone said. “Hopefully we’ll get to meet him a little bit tonight. We’ll get Trevi [catcher Jose Trevino] with him tonight, make sure they connect and then we’ll do what we have to do to get with him. We’ve had a ton of conversations with him and he’s been great. I feel like we’re in as good a spot as we can be without having him here yet. But yeah, a little weird.”

Montas, who spent time on the injured list earlier this season with a shoulder issue, threw 53 pitches in his return July 21 and 78 pitches in his next start on July 26. Boone said Montas, 4-9 but with a 3.18 ERA in 19 starts, will be brought along gradually.

“I don’t even think I’d go that far with him,” Boone said of the 78 pitches. “Especially with tomorrow being his 10th day since his last outing. So he’ll definitely be shorter tomorrow. It’ll be a couple [of starts] to get him built back up to that full starter workload.”

Stanton latest

Boone said Giancarlo Stanton, on the IL since July 26 with left Achilles tendinitis, continues doing light on-field work — which includes hitting off a machine, running and throwing — but didn’t want to put a timeframe on his return.

“I don’t want to put a time on when he’s going to be back, because anything is possible,” Boone said. “Bottom line is he’s trending in a good direction right now. I don’t think G or I necessarily want to get tied into a day that we’re looking at.”

Astros closing in

The Yankees have a half-game lead over the Astros in the battle for the American League’s best record. On June 18, when the Yankees were 49-16, they were nine games ahead of Houston, but they’ve gone 21-22 since then. On July 8, they were 61-23 and still had a 5 1⁄2-game lead, but they’ve gone 9-15 since then.

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