Dylan Cease has taken the ball every fifth or sixth day for the last five years. Yu Darvish hasn’t quite been himself since returning from his elbow injury. Michael King is just one start into his return from knee inflammation.

So it made sense to insert JP Sears on Friday to give the rotation one last break before the Padres’ final postseason push.

Of course, a playoff-caliber offense beating up on baseball’s worst pitching staff was part of the calculus.

Not much went according to plan.

A four-run fourth inning gave the Rockies their first runs of the year at Petco Park, Sears could not finish the fifth and the Padres were largely quiet after Manny Machado’s first-inning homer in a 4-2 loss to the 107-loss Colorado Rockies in front of a sellout crowd of 40,014.

At least there was the potential for late-inning drama as the Padres brought the tying run to the plate in each of the last three innings.

But they sat down in order after the first two batters reached in the seventh, pinch-hitter Will Wagner’s double-play ball up-ended the eighth inning and Ramón Laureano’s ninth-inning groundout was all they could muster in the ninth after Machado singled and Gavin Sheets doubled with one out off Victor Vodnik.

Jackson Merrill even walked with two outs to bring the go-ahead run to the plate but Ryan O’Hearn struck out to end the game.

Sears’ trouble seemingly came out of nowhere.

He struck out two in the first inning, two more in the second and then three in a row in the third after a leadoff walk to Kyle Farmer gave the Rockies their first base runner.

Then Hunter Goodman singled to start the fourth and Jordan Beck followed with a single. After a sacrifice bunt and Sears’ eighth strikeout — one shy of a season high — the 29-year-old left-hander grooved a middle-in sweeper for Blaine Crim yank out to left, some 439 feet from the plate.

Then Kyle Farmer pulled Sears’ next pitch—a middle-in fastball—out to left.

Just like that, the Padres were in a 4-1 hole, courtesy of the first runs the Rockies had scored all year at Petco Park.

The Padres outscored Colorado 16-0 in a sweep here in April and won 2-0 on Thursday.

The home runs were also the fifth and sixth that Sears has allowed in 19 innings (6.16 ERA) in four starts spread across three stints since the trade deadline.

A 4-1 hole — at least these days — was far too deep for a scuffling offense to dig out of.

The Padres, after all, had scored more than four runs at or about sea level just once since Aug. 31 and they lost that game, 7-5, as the Orioles completed a sweep to finish the previous homestand.

They scored 18 runs over their final two games in the thin of Coors Field last weekend, won a 4-3 walk-off on Monday and had scored just five runs over their last three games when Machado homered in the first inning.

The blast was his first hit of the homestand and his third homer in his last ninth games. But he entered the weekend hitting .188/.248/.289 since Aug. 1 and his manager defending the decision to allow Machado to continue to play through this slump.

Machado has started every game this season and hasn’t had a DH day since Aug. 18.

“We’re both professionals … so I’m not going to talk Manny into anything,” Padres manager Mike Shildt said of an ongoing conversation about rest for his 33-year-old third baseman. “I’m going to have an adult conversation with a guy that’s posted for us all year. This team’s gone through, like every team has gone through their trials and tribulations,  but when you have guys that are there day in, day out, through those trials and tribulations, those guys are really, really important.

“Manny Machado is at the top of that list for this club. … He’s come out early (to work) the last couple days. If he was tired, he’d be sleeping.”

Tanner Gordon — who yielded Machado’s last home run on Sunday in Denver, one of three off him in that game —responded to the first-inning homer by retiring the next 16 batters.

Luis Arraez broke up that run with a single to start the seventh and a walk to Machado ended Gordon’s night. But reliever Juan Mejia retired the next three hitters — a Ramón Laureano strikeout sandwiched by flyouts form Gavin Sheets and Jackson Merrill — to squash the first semblance of a rally.

The first two hitters reached in the eighth inning, too, but Jimmy Herget got Wagner to bounce into a double play and handed Fernando Tatis Jr. his fourth strikeout of the game.

Afterward, a smattering of boos serenaded Tatis’ walk back to the dugout.