ILB Demorrio Williams celebrates as he returns an interception 59 yards for a TD. San Diego's defense scored two touchdowns in a 31-13 win over the Chiefs. (US Presswire)

The defense gave San Diego a much-needed lift by scoring two touchdowns as the Chargers (4-4) took down the Chiefs 31-13 on Thursday Night Football.

In recent games, QB Philip Rivers has struggled and missed key targets, and two Chargers wide receivers -- Eddie Royal and Robert Meachem -- were inactive due to hamstring injuries against the Chiefs (1-7). Another receiver with a hamstring injury, Richard Goodman,  was placed on injured reserve on Monday.

This left WR Malcom Floyd as the only receiver Rivers had completed a pass to this season. Danario Alexander and Seyi Ajirotutu were the other active receivers. Alexander signed last week and Ajirotutu on Monday. Neither had caught a pass this season.

Still, Rivers completed 18 of 20 passes for 220 yards and two TDs with a passer rating of 125.0. The performance marked the sixth time in NFL history a QB completed 90 percent of his passes in a game with 20 or more attempts.
 
Ajirotutu extended the Chargers' first drive with a 28-yard diving reception on a third-and-5 situation. “If he doesn’t come down with that ball, we would have had to punt,” Rivers said. “It was an unbelievable catch.”

TE Antonio Gates capped the drive with a 14-yard TD catch.

Rivers' only two incompletions came late in the second half. He threw the ball out of the back of the end zone on first-and-goal from the 8-yard line. Two plays later, with the Chargers on the 1-yard line, Chiefs S Eric Berry picked off a pass in the corner of the end zone that was intended for TE Dante Rosario.

“That was just a terrible play,” Rivers said. “No other way to describe it. I know better.”

The mistake left the Chargers with a 10-3 lead going into the half. But Rivers found Floyd for a 13-yard TD to give the Chargers a 17-6 lead at the start of the fourth quarter.

The defense then took over and put the game away.

OLB Jarret Johnson sacked Chiefs QB Matt Cassel in the end zone. Cassel fumbled and the ball was recovered by OLB Shaun Phillips for a touchdown.

It was only the second sack for Johnson, who joined the Chargers as a free agent from the Ravens this season. “It was huge to make a big play like that,” Johnson said. “It feels good. I needed that.”

ILB Demorrio Williams ended the Chiefs' next drive when he intercepted Cassel and returned it 59 yards for a TD. Williams was another free-agent addition -- he played for the Chiefs last year -- but he hadn't made much of an impact this season before Thursday night.

With the win, embattled general manager A.J. Smith and coach Norv Turner will keep their jobs for at least a few more weeks. It was widely speculated both could have been fired if the Chargers had lost a fourth straight game.

“I think we want to win for [Turner] every week,” Rivers said after the game. “We play for our coach.”

Rivers insisted the environment around the team has not been chaotic with Smith's and Turner’s jobs apparently on the line.

When the game turned: FS Eric Weddle fumbled a punt return that was recovered by Chiefs LB Cory Greenwood on the Chargers 24-yard line with the score still 10-3 near the start of the third quarter. The Chargers defense held the Chiefs to a three-and-out and Kansas City PK Ryan Succop missed a 39-yard field goal.

Highlight moments: Phillips' fumble recovery for a TD and Williams' pick-6 secured the game for San Diego.

Top-shelf performances:

  • Chargers TE Antonio Gates: Caught all three passes thrown his way for 43 yards and a TD. Gates has 79 career TD receptions and needs just two more to match WR Lance Alworth (81) for the franchise record.

  • Chargers WR Danario Alexander: Three catches on three targets for 61 yards.

Head scratcher: Chiefs coach Romeo Crennel elected to kick a 49-yard field goal instead of running a play on third-and-1 from the Chargers' 31 in the second quarter. San Diego had a 10-0 lead at the time. This was probably the right call, but perhaps Crennel should have gone for it to give his struggling team a boost.
 
What they said about Rivers' INT:

  • Chargers coach Norv Turner -- “We thought we had a chance to get a touchdown with the play-action. It’s a ball he should have thrown away.”

What they said about safety Eric Berry's interception:

  • Berry --“I knew they were going to come at me because of the last game and the first drive. I told myself that I would not budge. I told myself I was going to keep swinging. I just kept playing ball and they came at me and I picked it off.”

What they said about the contributions of Jarret Johnson and Demorrio Williams:

  • Turner -- “Those guys have been good football players through the first half of the season. Then, in different situations, you get opportunities to make big plays. If you get those opportunities, you [better] take advantage of them, and that’s what happened tonight.”

Injury update: Chiefs -- G Jeff Allen (head) and RB Jamaal Charles (neck) exited the game. Chargers -- RB Ryan Mathews tweaked a leg but returned to the game. Turner will give an injury update on Friday for San Diego.

Going forward: Chargers -- In Week 10, they will travel to take on the Tampa Bay Buccaneers (3-4). Chiefs -- They will make one last stand at relevancy in Pittsburgh against the Steelers (4-3) on Monday Night Football.

Follow Chargers reporter Dan McLellan on Twitter @CBSChargers and @sandiegosports.