SAN DIEGO — The start of the final four games arrived with a thud for the San Diego Chargers.

They christened a season-defining run of four games by losing to the New England Patriots 23-14 on Sunday. Despite or because the Patriots pulled it out in the final moments, it was obvious the Chargers were still regretting that the big opportunity slipped away.

The defense played well enough and even added a touchdown of its own.

But with the offense struggling behind a shaky line, San Diego (8-5) was no match for New England (10-3).

If the Chargers want to lick their wounds, they can’t take much time doing so.

With an AFC West showdown against the Denver Broncos next on Sunday and then two testy season-ending road trips to San Francisco and Kansas City, the Chargers need to focus forward.

Whatever hopes the Chargers had of catching the Broncos in the AFC West standings took a blow. The Chargers are two games out with three to play, with their most likely playoff entrance being the wild card route.

But there is also a pack of teams ready to claim that invitation.

So the Chargers have to get right, quickly. And that was the message Monday.

Although one last look back sums it up.

“Too many little mistakes that added up and cost us at the end,” coach Mike McCoy said.

“We got to play better as an offense,” McCoy said. “That was not our best day. They did a nice job and that is a very well coached football team. But it’s about us because we’ve got a huge game coming up this weekend.”

Now, the Chargers must look for what to take away from that loss to help them move forward. After all, the next three opponents will see the tapes, too. And it wasn’t all bad.

The video will show that the Chargers stymied the mighty Patriots on a couple of defensive fronts. New England got inside the Chargers 5-yard line on two occasions and collected by six points. Then in the third quarter, the defense forced the Patriots into punts in four straight series.

“We definitely are proud of how we played but it just wasn’t enough,” cornerback Shareece Wright said, “We need to get better. We need to make one more play and we didn’t. That was the difference. We just needed one more play. We had four straight three-and-outs and it still wasn’t enough.”

–The Chargers are holding punting auditions after Mike Scifres suffered a broken collarbone on what may have been a game-turning play — a blocked punt. Scifres was scheduled for surgery Monday.

Kicker Nick Novak hadn’t punted since high school before he was called upon on Sunday. He averaged 40 yards on six punts.

“The switch just turned on,” Novak said of seeing Scifres being carted off the field. “I spent a lot of time on it when I was a kid and in high school. It’s something I knew I had in me.”

–One game after the Chargers had a franchise-first four receivers with 80 yards or more, Malcom Floyd paced the passing game with 54 yards in receptions. The Patriots’ secondary is among the game’s best and proved it again against the Chargers.

“That’s one of the best defensive back groups in the league, in my opinion,” said wide receiver Eddie Royal, who had two catches for 30 yards. “Those guys get in your face. They play tight coverage. Every ball is going to be contested.”

Notes: Tight end Ladarius Green was concussed and will be evaluated this week. . . . Running back Ryan Mathews is worth watching as he walked with a limp during the second half. . . . Offensive lineman Jeff Baca was released as was cornerback Kendall James from the practice squad.

REPORT CARD VS. PATRIOTS

–PASSING OFFENSE: D — Quarterback Philip Rivers was off and there were many reasons for that. The pass protection was shaky as Rivers was harassed and/or sacked most of the game. The receivers had trouble getting separation, which didn’t help Rivers. And the running game wasn’t enough to keep the Patriots’ pass rushers honest. Rivers’ 189 passing yards was his second-lowest total of the season.

–RUSHING OFFENSE: D — The Chargers couldn’t crack 55 rushing yards, which was surprising after a good start. Ryan Mathews was running hard and there were some creases for him, but the Patriots second-half adjustments shut the door.

–PASS DEFENSE: B — Still not much of a pass rush as Tom Brady had plenty of time to go through his reads. But the Chargers did stone him twice when he was inside the San Diego 5-yard line by knocking down passes or creating pressure. But in the end Brady threw for two touchdowns and 300-plus yards. An interception by Manti Te’o was big at the end of the half but the Chargers didn’t capitalize.

–RUSH DEFENSE: B — The early returns weren’t good here as the Patriots moved the ball easily on the ground. But those early-down runs that were putting Tom Brady in manageable third-down situations started to dwindle as the game progressed. Good stuff by linebacker Kavell Conner as he was stout in the run defense.

–SPECIAL TEAMS: D — When you get your punter injured, it’s tough to get a good grade. Donald Butler whiffed as the up blocker on a punt, and Brandon Bolden blocked the punt and hit Mike Scifres so hard he broke his clavicle. Nick Novak did OK filling in, but early on the Chargers were losing the field-position game. The Chargers still have a tepid return game, but coverages were decent.

–COACHING: F – Coach Mike McCoy always says it’s all about winning and losing, nothing else matters. So he gets the black mark as not only did his players not produce at a high level but many mentioned the adjustments the Patriots made caused the Chargers to doubt themselves. Also McCoy’s decision to punt at midfield, down by two scores with six minutes remaining, was a head-scratcher. He said he trusted his defense more than his offense at that point, which is true. But giving the ball back to Tom Brady was the final nail in the Chargers’ loss, which snapped a three-game winning streak.