The San Francisco 49ers face their biggest test of the year so far when they meet the Dallas Cowboys in primetime on Sunday.

San Francisco has strolled to a 4-0 record in hugely impressive fashion, but the Niners have yet to face an opponent of the caliber of the 3-1 Cowboys.

The Niners have ended each of the last two Cowboys seasons with victories in playoff matchups, and this encounter at Levi's Stadium could well prove to be a preview of another postseason clash between arguably the two best teams in the NFL through four weeks.

Dallas Cowboys (3-1) at San Francisco 49ers (4-0)
Date: Sunday, October 8
Time: 8:20 p.m. ET
Location: Levi's Stadium/Santa Clara, CA
Betting odds: 49ers -3.5, Over/Under 45
How to watch on TV: NBC
Streaming: FuboTV, YouTube TV, Network apps, etc.
Radio: KNBR 680 AM / 104.5 FM, 107.7 FM “The Bone" / SacTown Sports 1140AM

Can the 49ers get to Dak?

The 49ers have one of the premier defensive lines in football, one that got even better on Friday with the addition of former Cowboy Randy Gregory in a trade with the Denver Broncos.

Gregory won't play against his former team, though, and with the 49ers registering only one sack last week against the Cardinals, it's fair to wonder if the San Francisco pass rush can get home against a Dallas offense that, like Arizona, will rely heavily on quick game to negate the defensive firepower the Niners possess.

San Francisco's ability to get to Prescott will go a long way to determining the outcome of this heavyweight fight.

Will CMC keep rolling?

So much of the emphasis will be on 49ers quarterback Brock Purdy amid the increasingly ridiculous discourse about his superb start to the season.

The reality, however, is that if Christian McCaffrey continues his MVP-level start to the season, the Cowboys hopes of derailing the 49er offense will be very slim. Last year in the playoffs, Dallas did a good job of slowing down McCaffrey, limiting him to 57 yards from scrimmage, though he did score the game-winning touchdown.

McCaffrey is the focal point of the offense and, if the NFL's scrimmage yards leader manages to break free from the shackles the Cowboys placed on him last season, the 49ers will likely be on course for victory.

3 Players to watch

• QB Brock Purdy: It's impossible to completely ignore the Purdy of it all. Last season, the Cowboys gave the 49ers quarterback the sternest examination of a career that has yet to see him lose a game he has started and finished. He just about came through it, but there will be a spotlight on him again versus a ferocious defense that has talent to put him in extremely difficult situations.
• OT Colton McKivitz: San Francisco's starting right tackle struggled mightily in the season opener against the Steelers, conceding three sacks against T.J. Watt, and this week faces a similarly formidable challenge against Micah Parsons and a deep Cowboys defensive front. McKivitz has improved in recent weeks, only giving up two pressures in the last three weeks, and this clash will be litmus test of that progress.
• DE Drake Jackson: Both Jackson and Clelin Ferrell will be feeling more pressure to perform following Gregory's arrival, and there would be no better time for the former to rediscover the form that saw him record three sacks in Week 1 than on the primetime stage against an historic franchise rival in a game that could go a long way to deciding playoff seeding.

More 49ers news ahead of the game

• Randy Gregory trade looking like a steal before he's even played a game
• Christian McCaffrey taking after Frank Gore in feeling 49ers' Super Bowl push

49ers pass rusher gets chance to impress before Randy Gregory’s arrival

It’s his first chance to play since Week 1.