The undermanned Galaxy’s underwhelming season has ended with a whimper for a second consecutive year and change is in the air as the franchise approaches its final year with a soccer monopoly in Los Angeles before LAFC joins the MLS fray in 2018.

“Generally, a poorly played game,” said Arena Sunday following a loss on penalty kicks to the Colorado Rapids in the Western Conference semifinal in Denver.

It was an apt way for the Galaxy to end a generally poor season that never really got rolling.

Injuries prevented the star of the show in the opening game against the Rapids, Emmanuel Boateng, from a reprise, while Gyasi Zardes also remained sidelined, Landon Donovan left the game prematurely with an injury tightness and Robbie Keane was limited physically and unable to even take a PK.

An excessive amount of injuries may not have helped the Galaxy this year, but it was quality missing at both ends of the field that largely caused the club’s downfall.

Not surprisingly, Arena felt that was the case against the Rapids yet again.

To emphasize that, Arena threw young goalkeeper Brian Rowe under the bus in his post-game comments and yet again challenged Giovani dos Santos, who missed his penalty kick, to step up and take charge of the Galaxy next year.

“They have a very experienced goalkeeper and we don’t,” Arena said without noting the opposing goalkeeper was Tim Howard, arguably the best-ever American goalkeeper. “Maybe the difference was the goalkeeper today.

“Not much of a factor,” Arena added of dos Santos’ uninspiring performance. “He should be more demanding of himself to have a greater presence game in and game out.”

And next year he will have to step up more, especially if Gerrard and Keane leave, while Arena, too, is out of contract.

Given the two successive disappointing seasons following the Galaxy’s last MLS Cup — were Arena anything other than the most successful coach in league and, arguably, American soccer history — he may not well return either.

“I don’t talk about my contract,” Arena told the league’s website recently. “As of now I am (returning), but we’ll see.”

We will, indeed.

LAFC, which earlier this month said it had reached 10,000 season ticket deposits — about the same number of season tickets the Galaxy reportedly sold this year after two decades in MLS — may well provide greater business competition off the field than defunct Chivas USA ever did.

The Galaxy will need to step it up on and off the field to ensure Southern California’s fickle fans don’t decamp to the club’s soon-to-be rival.

Etc.

Despite the Galaxy’s season-ending loss, there is still live soccer in Southern California this weekend; the U.S. Women’s National Team concludes its year with a 6:30 p.m. game Sunday in Carson against Romania (live on Fox Sports 1). … The U.S. men, with the Galaxy’s Alan Gordon a late addition to the squad, take on dos Santos and Mexico at 4:45 p.m. Friday (live on FS1 and Univision) from Columbus, Ohio, in the opening game of the hexagonal, the final round of regional qualifying for the 2018 World Cup. … The U.S.-El Tri face-off isn’t the only World Cup qualifier in the next few days between bitter regional rivals: Brazil and Mexico meet at 3:35 p.m. today on BeIn Sports, while England and Scotland renew auld acquaintances in the world’s oldest international rivalry at 11:45 a.m. Friday on FS1. …Finally, this columnist is taking a break for the rest of this year; the column resumes in January.

For more local soccer news, read the 100 Percent Soccer blog at www.insidesocal.com/soccer.