There are still nine games remaining in the Major League Soccer regular season, and nine of 15 teams in each conference make the postseason. And in the Western Conference, 11 teams are separated by a mere 13 points in the standings.

So to say San Diego FC’s playoff hopes are slipping away, factually at least, is premature.

The eye test, though, says something else.

SDFC dropped a second straight home game, this time (yes) 5-0 against the surging Philadelphia Union and 16-year-old phenom Cavan Sullivan before an announced crowd of 21,171 at Snapdragon Stadium on Sunday night.

It’s the most lopsided defeat in the club’s two-year history, surpassing the 4-0 loss in March.

That was on the road against two-time defending Mexican champion Toluca at 8,750 feet. This was at home at sea level against a team that opened the MLS season with six straight losses and fired the coach.

“We started the match pretty well and maybe could have been up at least 1-0, maybe 2-0,” said coach Mikey Varas, whose team benefitted from a video review overturning a red card against midfielder Alejandro Alvarado late in the first half. “All of a sudden, the team collapsed.

“This is an unacceptable situation, an unacceptable result.”

Added captain Jeppe Tverskov: “Right now, it’s not clicking. That’s obvious.”

It was the second time in five days the azul and chrome have gone down 3-nil, and the second time in five days that their usually faithful fans have booed them, just as they did in the first half of Wednesday’s 3-2 loss against the San Jose Earthquakes, a team on an eight-game winless streak.

Philadelphia entered the night in ninth place in the Eastern Conference with 30 points, the same position and points as SDFC in the West. That’s where the similarities end.

Sunday’s win extended the Union’s unbeaten streak to 10. The last four, all victories, have been by a combined 15-1.

SDFC has now lost three straight by a combined 9-2 in the stretch run of a tight playoff race.

“There are two things,” Varas said. “One, when we don’t follow our principles and don’t play to our strengths, which is our style of play, and we start doing random things. The other one, which is even more important, is when we don’t fight and we don’t run and we get outworked.

“The foundation of anything in life if you want to be successful is hard work, commitment, pushing harder than someone else. It hurts a lot. It’s not who we are. You can say it’s a blip on the radar, but we take these blips very seriously. We need to self-correct very quickly, because it’s unacceptable.”

The hosts had the bulk of the possession through the opening 40 minutes, but the visitors gradually worked their way into the match and created the better chances until breaking through in first-half stoppage time with the kind of sublime skill that has people drooling over Sullivan, who, incredibly, doesn’t turn 17 for another two weeks.

Indiana Vassilev streamed down the left side and played a ball into the box to Sullivan, who blindly backheeled it diagonally toward goal. The ball rolled to the back post, kissed off it and nestled into the net.

“Ever since they got the goal, it was basically downhill from there,” Tverskov said. “Concede and concede and concede.”

Sullivan, who has a deal in place to join English giant Manchester City when he turns 18 next year, made it 2-0 in the 62nd minute. His tight-angled shot from the left side went through the legs of goalkeeper Duran Ferree, starting because regular CJ dos Santos was serving a red-card suspension from Wednesday against San Jose.

The Union got another goal six minutes later from Bruno Damiani, another in the 87th minute on an own-goal on a header by SDFC midfielder Anibal Godoy and another in stoppage time from 18-year-old rookie Malik Jakupovic.

The referee mercifully blew the final whistle immediately afterward, and the boos came raining down. As SDFC players walked toward what was left of the supporters’ section to thank them, one fan extended his arms with both thumbs down.

Milan Iloski, the San Pasqual High School alum who spent three tantalizing months with SDFC last season (and scored 10 goals in a mere 14 appearances), started up top for Philadelphia and nearly had a hat trick despite not scoring. His point-blank shot was deflected wide by an SDFC defender, he was poised to tap in Sullivan’s first goal when the ball hit the post first, and he had a hard shot in the second half bang off the crossbar.

SDFC (8-11-6) remains in ninth place in the Western Conference through 25 of 34 matches, which gets it into a play-in game – the winner of which plays at the conference champion a few days later.

But the LA Galaxy also have 30 points. Real Salt Lake, Minnesota United and Austin FC have 29 (and RSL has played one less match). Seattle sits in 14th place with 28 points but has played two fewer matches.

A bigger problem is SDFC’s schedule. Only three of its remaining nine MLS matches are at home, although given its recent form at Snapdragon Stadium, it might be better off on the road.

Next up is Wednesday night’s friendly against Mexico’s Tijuana Xolos in the Baja Cup, a game kept on the schedule despite the teams meeting here last month in the Leagues Cup between MLS and Liga MX.

Neither club is expected to use regulars (Tijuana’s coach has hinted he’ll play mostly youngsters). Fans almost certainly won’t see Xolos 17-year-old star Gilberto Mora, who was injured in their last league match.

And SDFC likely will be resting players for Sunday’s cross-country date at Inter Miami and Lionel Messi. Following that, it plays at Austin and the New York Red Bulls. The next MLS home match isn’t until Oct. 14 against Houston.

“I take full responsibility at the end of the day,” Varas said. “It’s my job to get the group ready to play, and for whatever reason, this group has not found any consistency.

“What I can promise is we’re going to go back the drawing board and we’re going to make the environment even more competitive because these guys have to fight for their lives if they want to be here. They have to show a lot more emotion.”