Biggest challengers to a Chiefs three-peat: No. 4, Brock Purdy’s 49ers

Editor's note: This is the second of a five-part series on the quarterbacks and teams best equipped to challenge Patrick Mahomes and the Chiefs and potentially stop them from becoming the first NFL team in the Super Bowl era to three-peat. No. 4 on our list: Brock Purdy and the 49ers. No. 5 was Jalen Hurts and the Eagles.

Once again, the 49ers faced the Chiefs in the Super Bowl. Once again, San Francisco built up a double-digit lead.

Once again, the Niners blew it.

That's the harsh reality San Francisco met in Super Bowl 58 six months ago, when Kansas City secured its second straight Lombardi Trophy. The Niners led 10-0 late in the second quarter, but heroics from quarterback Patrick Mahomes and tight end Travis Kelce helped fuel the Chiefs' dramatic 25-22 overtime victory, cementing their dynasty.

For the 49ers, it meant falling short on the biggest stage for the second time in five years.

"It's like one of the biggest heartbreaks you can deal with," wide receiver Deebo Samuel said.

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Entering the 2024 season, contract disputes have made the biggest headlines out of San Francisco. Star wide receiver Brandon Aiyuk's long-term status with the franchise has been unclear amid his hopes for a big-money extension. He's been subject to persistent trade rumors. Also not practicing is All-Pro left tackle Trent Williams, who's holding out while seeking a restructured contract.

If those two situations get resolved and both players are in the fold, the 49ers should once again be a Super Bowl contender. They'd return 19 of 22 starters from last season, including standout linebacker Dre Greenlaw, who could miss the start of the season recovering from the Achilles tear he suffered in the Super Bowl.

Quarterback Brock Purdy looks to build off a stellar second season, one that generated MVP buzz. He led the NFL in touchdown rate (7.0%), yards per attempt (9.6), passer rating (113.0) and QBR (72.8). The 2022 seventh-round pick was also third in passing touchdowns (31), fourth in completion rate (69.4%) and fifth in passing yards (4,280).

Even with Purdy's stunning ascension from "Mr. Irrelevant" status, superstar running back Christian McCaffrey is the true engine of the offense. Last season, he paced the league in touches (339), rushing yards (1,459), scrimmage yards (2,023) and total rushing and receiving touchdowns (21) en route to Offensive Player of the Year honors.

Why Purdy and the 49ers could beat the Chiefs in a potential Super Bowl LVIII rematch

In February's Super Bowl matchup, the chunk plays came in bunches for the 49ers early.

Their second play from scrimmage was a rollout pass to fullback Kyle Juszczyk for 18 yards. The next play, Purdy hit McCaffrey on a Texas route up the middle for 11 yards. After that, McCaffrey picked up 11 yards on a run up the middle. On the first play of the Niners' second possession, Purdy connected with Aiyuk on a crosser for 18 yards.

What did all those plays have in common? They featured 21 personnel, sets with two running backs and a tight end. San Francisco used that personnel grouping on 76.5% of their plays in the opening period, the third-highest rate in a game since 2016, according to Next Gen Stats.

The Niners didn't produce any points in the first quarter (a lost fumble on the opening possession and repeated penalties were the main reasons why), but it was otherwise their most efficient period in the game — seven first downs, 125 net yards, 6.5 yards per play.

Maintaining that heavy rate of 21 personnel could be pivotal for the 49ers in topping the Chiefs in a potential Super Bowl rematch.

After using the grouping on roughly three quarters of plays in the opening period, San Francisco didn't deploy it more than 57.1% of the time in each of the following four periods (second quarter through overtime), according to Sportradar. And Kansas City's elite defense showed vulnerability against 21 personnel in the 2023 regular season: Against that personnel grouping, the Chiefs allowed the most big plays in the league (15), the most rushing yards per game (32.1) and the seventh-most passing yards per game (24.3), per Sportradar.

While the 49ers scored all their points after the first quarter, they never matched their efficiency of the opening period.

Here's a breakdown of the 49ers' production by quarter in the Super Bowl.

First quarter [21 personnel on 13 of 17 plays (76.5%), per NGS]: 7 first downs, 1-for-2 on third down, 125 net yards, 6.5 yards/play, 1 lost fumble, 0 points
Second quarter [21 personnel on 7 of 14 plays (50%), per Sportradar): 5 first downs, 0-for-2 on third down, 64 net yards, 4.5 yards/play, 10 points
Third quarter [21 personnel on 5 of 14 plays (35.7%), per Sportradar]: 2 first downs, 1-for-4 on third down, 36 net yards, 2.5 yards/play, 1 lost fumble, 0 points
Fourth quarter [21 personnel on 8 of 14 plays (57.1%), per Sportradar]: 5 first downs, 0-for-2 on third down, 81 net yards, 5.7 yards/play, 9 points
Overtime [21 personnel on 5/14 plays (35.7%), per Sportradar]: 4 first downs, 1-for-2 on third down, 76 net yards, 5.4 yards/play, 3 points

A second key for the 49ers to beat the Chiefs is running McCaffrey more — to the left.

In last season's Super Bowl, he had a game-high 80 rushing yards — but on an underwhelming 3.6 yards per carry. He was much more effective running to the left than he was to the right — 13 carries for 61 yards (4.6 yards per carry) headed left, compared to nine carries for just 19 yards (2.1 yards per carry) headed to the right, according to Pro Football Focus. His costly opening-possession fumble also occurred when running to the right.

Those splits continued a trend from the regular season, when McCaffrey was also much more productive running to the left. The All-Pro tailback averaged 5.8 yards per carry running to his left (157 carries for 921 yards and 10 touchdowns) compared to 4.4 yards per attempt going to his right (110 rushes for 484 yards and three touchdowns), per PFF. So McCaffrey's comfort level is evident going to his left, where Williams — arguably the best left tackle in football — controls the edge.

In a potential Super Bowl rematch, that's where the 49ers have to attack.

That's where they can potentially avoid even more heartbreak on the biggest stage.

Five teams that can prevent a Chiefs three-peat

Ben Arthur is the AFC South reporter for FOX Sports. He previously worked for The Tennessean/USA TODAY Network, where he was the Titans beat writer for a year and a half. He covered the Seattle Seahawks for SeattlePI.com for three seasons (2018-20) prior to moving to Tennessee. You can follow Ben on Twitter at @benyarthur.

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