Yankees pitcher James Paxton reacts during the third inning against the Colorado...

Yankees pitcher James Paxton reacts during the third inning against the Colorado Rockies at Yankee Stadium on Sunday. Credit: Brad Penner/Brad Penner

There are days when a Yankees starter gives up four or five runs, the lineup scores six or seven, and everyone just keeps happily motoring toward October.

It’s felt that way for a while now. The inevitability of the playoffs, the nearly certain AL East title. The Yankees usually are good enough, and deep enough, to overcome whatever adversity pops up in their path. Most days, roughly 67% of them, end up as a Yankees victory.

Sunday against the Rockies, however, was not one of them.

James Paxton was flat-out lousy, and his first-inning hex continued when Charlie Blackmon drilled his second pitch into the Yankees’ bullpen. Paxton stuck around only long enough to record one out in the fourth and wound up allowing seven runs — four earned — in the Yankees’ 8-4 loss to the Rockies.

“I just didn’t locate very well,” he said. “Didn’t execute. It’s on me.”

On another steamy afternoon (first-pitch temperature: 94 degrees), the Yankees looked listless and weren’t able to bail out Paxton despite hitting three homers. That was a rarity in itself. Before Sunday, they were 40-5 when smacking at least two, so you can see how forgiving their offense typically is for any pratfalls by their pitching staff.

Despite Brian Cashman’s admission that the team is searching for rotation help, the Yankees’ 2.59 ERA this month had been the best in the majors before Sunday, so it’s not as if they are in the midst of a full-blown crisis. We’re not sure how serious the issue actually is, but it’s safe to say Cashman would feel a whole lot better if Paxton and J.A. Happ pitched more to his offseason projections.

The Yankees already have shown they have the weapons to claim the AL East and even hold off the Dodgers, Twins and Astros for home-field advantage throughout October. This group has managed to occupy that spot even with Domingo German (3.45) being the sole starter with an ERA below 4.00 (excluding Chad Green’s 2.31 in eight opener assignments).

To put that in context, there are only 15 qualified starters in the AL with ERAs better than 4.00 — and only the Astros, Rangers, Twins, Indians and Athletics have as many as two of them. The Yankees have a significant advantage in the bullpen department, with the AL’s top WAR (5.3), the second-best ERA (3.76) and three closer-caliber relievers for the back end.

Paxton is sort of the swingman in the rotation, in the sense that he could really move the confidence needle, improve the whole feel, if he would pitch regularly to his ceiling. At the moment, he is penciled in as the Yankees’ No. 2 playoff starter, behind Masahiro Tanaka, and with the surprising Giants (i.e. Madison Bumgarner) climbing into the wild-card hunt, it doesn’t seem as if Cashman is going to get another No. 1 in the trade market.

The Yankees need Paxton, obviously, for a World Series run. They’d prefer not to have to merely survive him during the next two months. Fortunately for them, he has plenty of time to restore any shaken faith.

As usual, Aaron Boone defended him at the postgame mic, blaming Paxton’s inconsistency on his stint on the injured list because of knee problems. The manager even brought up the heat as a contributing factor to Sunday’s fade.

Luke Voit’s error opened the door for those three unearned runs in the third inning, but we’ve been led to believe that Paxton is equipped to mitigate the damage in those volatile situations, not spray gasoline onto the sparks. For a team with designs on a World Series crown, Paxton can’t turn out to be Sonny Gray 2.0.

“Overall, I think I look at him as a guy we’re going to lean on down the stretch,” Boone said, “and hopefully into October.”

Boone has to be right about Paxton. German is saddled with innings-limit concerns, Happ has been a disappointment and CC Sabathia is getting by on fragile knees. As for Luis Severino, who still hasn’t thrown a pitch this season, he’s a long shot.

Cashman should be able to get someone like Marcus Stroman to solidify the rotation, but Paxton shouldn’t think he’s just along for the ride here.

“It’s been up and down, you know?” he said. “Just been having trouble finding that consistency.”

Throw out Sunday as one of those rare Yankee downers in this special season, but only if Paxton is able to provide significantly more ups in the future.

Newsday LogoSUBSCRIBEUnlimited Digital AccessOnly 25¢for 5 months