PHILADELPHIA — It took until the fifth inning for the Padres to be out of Monday’s game.

Then it got worse. And there would be no almost-comeback this time.

The Padres are struggling mightily to score runs and failing miserably in keeping their opponents from scoring runs.

Monday’s 9-2 loss to the Phillies in the opener of their series at Citizens Bank Park kept the Padres winless through the first four games of this six-game road trip.

“It’s been tough,” Manny Machado said. “Tough stretch here.”

At least as troubling as the losing streak, which has dropped them from two games over .500 to two games under, is the Padres’ run of poor starting pitching.

Randy Vásquez was the latest starter to get pummeled, though he lasted longer than the 3⅔ innings turned in by Adam Mazur on Saturday and Dylan Cease on Sunday. Nonetheless, he hardly gave his team any more of a chance, leaving with one out in the fifth inning and the Phillies up 6-1.

That followed the Padres trailing 7-1 after four innings on Sunday against the Mets before a late burst made the game close for about five minutes.

“This league is based on pitching,” Padres manager Mike Shildt said. “We have a good offense, and I like our offensive approach. But if you don’t have consistent starting pitching, you’re going to have a hard time being a consistent club that’s going to shake hands (after games) because it compromises your bullpen, and you get down. And it’s a tough league to be down consistently.”

On Monday, the Padres’ defense helped Vásquez avoid trouble for a bit. But the team leading the National League in runs scored per game could not be contained for long.

Padres catcher Kyle Higashioka threw out Kyle Schwarber trying to steal second base to end the first inning, and three excellent plays helped Vásquez immensely in the bottom of the second inning.

As they did in each of the first six innings, the Phillies put the first batter of the inning on against Vásquez. But after Alec Bohm’s single, left fielder Jurickson Profar ran 111 feet to make a sliding catch, stopping with the ball in his glove just in front of the tarp rolled up alongside the side wall in foul territory.

Nick Castellanos followed with a double to the gap in right-center field that Jackson Merrill fielded on a bounce off the wall and threw to shortstop Ha-Seong Kim, whose throw to Higashioka was just in time to get Bohm.

The next batter, Brandon Marsh, hit a hard grounder to the right side. Jake Cronenworth knocked it down with a dive, keeping Castellanos from getting past third, and Vásquez escaped with a strikeout of David Dahl.

The defense could not save Vásquez in the third, because defenders are not allowed to play 444 feet from home plate.

That is how far, after Rafael Marchán knocked a 78.2 mph flare into left-center field to lead off the inning, Kyle Schwarber launched a ball at 108.1 mph to the Phillies bullpen beyond center field.

The bottom of the fourth inning began with Vásquez walking Marsh, who advanced to second on a wild pitch, to third on a groundout to the right side and scored on another flared single by Marchán.

The Padres scratched out a run, to get to 3-1, in the top of the fifth inning. It came with help from Marsh, the Phillies center fielder, who booted a single by Machado, allowing Machado to hustle to second. He moved to third on a long fly ball by Donovan Solano and scored on Cronenworth’s groundout.

That was the last time the game was close.

Vásquez had gotten out of the fourth with a double play grounder by Schwarber, but the fifth spiraled from the start.

Trea Turner led off with a single, Harper doubled and Bohm homered to make it 6-1.

After getting an out and surrendering a double, Vásquez (1-4, 5.70) was replaced by Adrián Morejón.

The left-hander ended that inning before giving up Marchán’s third single to start the seventh and then surrendering Schwarber’s second homer.

Profar led off the seventh inning with a single and scored on Solano’s one-out double before Phillies starter Christian Sánchez (4-3, 2.91) made it through the inning to complete his night.

The offense bears some blame for the recent travails. Monday was the third time in four games the Padres scored one or two runs. They lost the first of those 2-1 on Friday. A 5-1 loss followed Saturday before Sunday’s 11-6 defeat.

But there simply is no discounting the difficulty of getting out of the kinds of holes the Padres have faced recently, in particular the past two days. Across the major leagues this season, a team that has been down by five or more runs has come back to win just 19 times, and the Padres are tied for the MLB lead with two of those victories.

“We’ve shown the ability to come back,” Cronenworth said. “Can’t do it every night. We were there. … Then they come and score three and then they blow it open. It’s tough to win when you have eight hits and they have 18.”

But the Padres have scored one run in the first five innings in each of their past four games.

“It just seems that every sixth thing is when we score,” Cronenworth said. “I don’t know why that is. Score those runs early and give our pitchers a little bit of breathing room to go out there and do what they do, that’s something we can get better at.”