SAN DIEGO — Welcome to the playoffs, but aren’t the San Diego Chargers getting a jump on things?

Not so, according to quarterback Philip Rivers, as San Diego prepares for Sunday’s visit from the St. Louis Rams.

“We know what is ahead,” Rivers said. “We have what I think is a playoff team coming in St. Louis this week and the rest of them all are.

“It is a playoff mindset from here on and shoot, not that it hasn’t been, but that is just natural when you get to this point in the season. You can’t be blind and not realize that’s what we have ahead of us.”

The Chargers have behind them a three-game losing streak, thanks to sneaking past the Oakland Raiders, 13-6, last week.

But the uneven Chargers, despite the win, didn’t quite pass the eyeball test after having an extra week to prepare.

The offense — 13 points and one touchdown in two games — remains unsteady.

The defense did well on Sunday, but was that due in part to how horrible the Raiders played?

Maybe.

But it’s clear if the Chargers are to navigate a schedule which, after the Rams, has the Baltimore Ravens, New England Patriots, Denver Broncos, San Francisco 49ers and Kansas City Chiefs, they need to pick up their game.

“Offensively, the last eight quarters hasn’t been our best eight quarters,” Rivers said. “Thankfully we got out of there 1-1 in those eight quarters. If you can score 13 points in two games, what would you think your record would be? Probably 0-2. That is 6 1/2 points a game and you don’t win many of those.

“But our defense played awesome on Sunday and it is a team deal. There might be a game in the next stretch it needs us to score a bunch of points and we have to answer the bell and do that.”

Rivers knows the challenge is grand this week. He twice looked compromised after taking big hits against the Raiders and now here comes the sack-happy Rams.

Rivers made the injury report for the first time in recent memory with a chest ailment on Wednesday. He’s there because of teammate Antonio Gates spilling the beans on Sunday that Rivers have been playing with a “severe rib injury” recently.

Rivers said he is fine. And despite how the Chargers played in their last outing, they could be alright as well.

“Sometimes it is the games that aren’t as pretty that can propel you forward,” Rivers said. “And we are hoping that is the case.”

SERIES HISTORY: 11th regular-season meeting. Rams lead the series, 6-4. The teams both used to call Los Angeles home and might do so again in the future. But they’ve only met 10 times. The Chargers haven’t defeated the Rams since 2006, in Rivers’ first year as a starter. In winning, 38-24, Rivers threw for a touchdown and 206 yards. The Rams took the last meeting, which came in St. Louis in 2010.

MEDICAL WATCH:

— OLB Dwight Freeney didn’t work on Wednesday, as is his custom. He will play on Sunday.

— NT Ryan Carrethers (elbow) didn’t practice after leaving Sunday’s game.

— C Rich Ohrnberger (back, ankle) didn’t practice and he could be iffy for Sunday. Even if he does play, him making it through the game could be a stretch.

— QB Philip Rivers (chest) was a full participant.

GAME PLAN: The Chargers are going to focus on being successful on the early downs, otherwise the Rams pass rush gets to tee off on Rivers. With Ryan Mathews showing no setbacks after returning to action last week, the Chargers will lean on him. If they can run the ball — or have Rivers flip short passes in the flat — the team hopes that keeps Rivers from third-and-longs on too many occasions.

MATCHUPS TO WATCH:

— Chargers pass protection vs. Rams pass rush: Rivers was sacked twice in the last game but hit nine times. And twice it looked as if he was close to exiting the game because of those hits. In the Rams, the Chargers will need to keep in an extra blocker to make sure Rivers isn’t bounced around again. There is concern inside with the availability and skill level of the players. But the edges have to be clean too, and that is a chore when wrestling with Robert Quinn and William Hayes. The tackles, D.J. Fluker and King Dunlap, need to be sharp. And the Chargers’ fingers are crossed that center Rich Ohrnberger can play so they don’t have to count on a rookie, Chris Watt, to replace him.

— Chargers run defense vs. Rams running game. The Rams figure to want to play keep-away from Rivers by running the ball and keeping the score low. They aren’t interested in getting into a shootout, not when matching Shaun Hill vs. Rivers. The Chargers must contain Tre’ Mason as the rookie is coming off his first 100-yard game. Mason got the ball 29 times, the most any Ram has carried the ball this season. It makes sense that the Rams will use that same ball-control offense to keep Rivers — like last Sunday with Peyton Manning — off the field. The Chargers’ run defense got a boost with the return of Manti Te’o. But really it has been the play of inside linebacker Kavell Conner, and to a lesser degree, Andrew Gachkar, that has led the Chargers’ improved run defense.