SAN DIEGO — Instead of the Chargers preparing for a playoff game, they were exchanging cell phone numbers Monday.

It’s a rite heading into any offseason, and that was the Chargers’ destination.

Monday brought with it the realization that the season was kaput. The Chargers’ 19-7 loss to the Kansas City Chiefs on Sunday guaranteed that.

It was win-and-you’re-in, but the Chargers hit the eject button.

The Chargers had their playoff fate in their hands. All they had to do was beat backup quarterback Chase Daniel.

Instead the offense played as if it had two left feet, wasting another winning performance by the defense.

For the third time in four games, the offense chipped in exactly one touchdown.

“You’re usually not going to win if you do that,” quarterback Philip Rivers said. “And we didn’t.”

A team that was once 5-1 and atop the AFC West lost three of its last four and fell flat.

“That was not good enough,” coach Mike McCoy said. “That’s unacceptable.”

But it happened and — just like that — the Chargers start a game nobody wants to play: Digging into a season that resulted in the Chargers missing the playoffs for the second straight year.

“Those are all the what-ifs,” Rivers said. “We fought to the end and won nine football games. We needed to win one more.”

The Chargers have plenty of needs, and that was proven by their 3-6 record against teams with winning records. But it doesn’t sound as if a rebuilding process is coming.

“We’ve got to win now,” McCoy said. “Yeah, I believe in building a team, but I want to win starting tomorrow.”

NOTES: OLB Dwight Freeney pulled down Kansas City QB Chase Daniel for his fourth sack of the season and the 112th of his career, and there’s speculation that it might have been his last. His contract expires. … The Chargers’ 2015 home opponents (other than the AFC West) are the Cleveland Browns, Pittsburgh Steelers, Miami Dolphins, Chicago Bears and Detroit Lions. Their non-division road foes are the Baltimore Ravens, Cincinnati Bengals, Jacksonville Jaguars, Green Bay Packers and Minnesota Vikings.

REPORT CARD VS. CHIEFS

–PASSING OFFENSE: D-minus — Only some success from Philip Rivers lifts this grade from the bottom. Rivers has played better; he turned the ball over three times. But he was under siege every time he attempted to pass, as seven sacks proves. The pass blocking was horrendous, which meant the receivers couldn’t get open. The Chargers were 2 of 11 on third downs as they consistently were turned back on nearly every big passing opportunity. Eddie Royal was solid; Antonio Gates and Malcom Floyd were misused the whole game.

–RUSHING OFFENSE: B-minus — Whenever one of the NFL’s worst running attacks passes 100 yards, it’s noteworthy. The Chargers tried to prove early that they were going to lean on the running game and, for the most part, it was working. Branden Oliver had 71 yards and a score on just 14 carries. But when the team needed a yard to keep its playoff hopes alive, it was unable to deliver.

–PASS DEFENSE: B- — Backup quarterback Chase Daniel couldn’t miss early, but the Chargers’ secondary kept him under 160 yards and held him to one touchdown that was ruled a fumble recovery. But the Chargers were unable to snatch a takeaway from Daniel, which was a goal considering how bad the Chargers’ offense is playing. Depth showed up as the Chargers lost defensive backs Shareece Wright, Marcus Gilchrist and Jahleel Addae to injuries.

–RUSH DEFENSE: B — The Chiefs love to run the ball but the sledding was tough against the Chargers. Jamaal Charles running on one leg (54 yards) might be part of it but the Chargers’ run stuffers were keen, especially in the red zone. Manti Te’o continues to show growth and Corey Liuget was steady, as usual.

–SPECIAL TEAMS: D — The coverages were tested time and again by D’Anthony Thomas. The return game hasn’t shown up all year, and that was no different in Week 17. Nick Novak was asked to kick a 52-yarder at a critical juncture, but he missed. On a day when the offense needed some help with field position, the special teams didn’t contribute much.

–COACHING: F — The Chargers were consumed by the pass rush, but that wasn’t a secret considering the matchup. Whatever adjustments were made weren’t noticeable as the Chiefs racked up sacks throughout the game, finishing with seven. But what will be remembered is Mike McCoy and coordinator Frank Reich calling for running plays behind a decimated line with third-string running back Donald Brown. Not much imagination or flexibility was shown throughout the game — an odd mix of plays. Coordinator John Pagano’s defense carried more than its share while again shinning in the red zone. But, again, the tepid offense didn’t allow it to be a winning effort.