(CBS Denver) — The Denver Broncos have stumbled to an 0-4 start to the season. Despite new quarterback Joe Flacco, the two-back running attack of Phillip Lindsay and Royce Freeman and a serviceable defense, the Broncos can’t seem to find the win column. Two of their losses were decided by a two-point margin. Had those last-second field goals not occurred, the conversation surrounding this team would sound very different. The Broncos’ search for answers continues in Los Angeles, where they’ll face their AFC West rivals in Week 5.

The Chargers sit at 2-2, as they make their way through an early season similarly filled with struggles. Injuries have been their main concern, with at least a dozen important players ailing. Wide receiver Mike Williams and tight end Hunter Henry are among the many players missing time so far. Defensive end Melvin Ingram can now be added to the list, though running back Melvin Gordon, whose holdout ended last last Thursday, should now be available Sunday. Setting aside their Week 4 win over the DOA Miami Dolphins, the Chargers are 1-2 in three games decided by a touchdown or less.

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Both the Broncos and the Chargers need a win this week to keep up with the undefeated Kansas City Chiefs. (The Oakland Raiders also pose a concern a quarter of the way through the season, though it’s hard to account for an erratic black and silver team that history suggests is due for an implosion.) This week’s matchup matters for both teams, beyond the typical early-October game.

The Broncos might be better than other win-less teams, but they certainly have their issues. Flacco, who was supposed to bring veteran leadership to this offense, has also imported his struggles from Baltimore. The offensive line hasn’t helped. Left tackle Garret Bolles, who has led the team in holding penalties since the 2017 season, continues to rack up the flags. But the problems stretch deeper than any one player. “The turnovers, the penalties, the missed assignments, the mental errors,” says Gannon, “that’s really what’s held back the Denver Broncos.”

Their rough start has led to discord for new coach Vic Fangio, who is trying to rally a locker room dotted with new faces. As NFL On CBS analyst Rich Gannon noted, “there was a quote from Chris Harris [Jr.] earlier in the week about, something to the effect of ’13 more weeks,’ which coming from one of your better players, one of the veterans on that defense, that’s not the type of message you want to get out there.” Harris is one of the team’s veterans, and should be thinking about getting his team’s first win rather than free agency.

Maybe defense can be the catalyst for turning around the season or at least finding that first win. Despite letting Jacksonville Jaguars Leonard Fournette run all over them, the Broncos had been solid against the run to that point. Containing Austin Ekeler and a possibly rusty Melvin Gordon will be critical against the Chargers. And after three sack-less weeks, the Broncos dropped Jacksonville Jaguars Gardner Minshew five times in Week 4, with Von Miller picking up two.

Philip Rivers doesn’t always respond well to pressure and can be forced into mistakes, or at least questionable displays of judgment. “The Chargers could easily be 4-0 right now,” according to Gannon. “Rivers has made a couple of poor decisions late in games. You go back to the Detroit game, where he tried to fit one in to Keenan Allen in double coverage. He threw a pick in the red zone the week before in a win against the Colts.” The Chargers ultimately prevailed in that Week 1 battle, after Rivers led a nifty overtime drive.

As goes Rivers, so go the Chargers. And he is having another solid season. Only the Detroit Lions held him under the 300 yards passing, and just barely. Keenan Allen remains his top target, with two 100-yard games, including a monster 183-yard, two-touchdown showing in a loss to the Houston Texans. His production should continue with Mike Williams still ailing.

Can he push his Chargers above .500, or will the Broncos finally find the win column?

The Broncos play the Chargers Sunday @ 4:05 ET on CBS.