The San Francisco 49ers are arguably the best team in the NFL, and it can also be argued who is most responsible for their success.

The Niners are 5-0 after demolishing the Dallas Cowboys, 42-10. Their point differential is plus-99, the highest in the league.

When he took over for Jimmy Garoppolo last year, quarterback Brock Purdy took the field alongside Christian McCaffrey, Deebo Samuel, George Kittle, Brandon Aiyuk, and a dominant offensive line. The Niners' elite defense also helps.

Purdy was the last player chosen in the 2022 NFL Draft and entered his first season as the third-string QB. But injuries to Trey Lance and Garoppolo put Purdy behind center, and Purdy has yet to lose a regular-season game.

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Brock Purdy raises his hand

Brock Purdy of the San Francisco 49ers reacts after a touchdown by Christian McCaffrey during the second quarter against the Dallas Cowboys at Levi's Stadium Oct. 8, 2023, in Santa Clara, Calif. (Ezra Shaw/Getty Images)

Considering how stacked the 49ers are, some might argue there are plenty of quarterbacks who could take snaps for San Francisco and they'd be just as dominant.

Don't suggest that to Rob Gronkowski, who says San Fran struck "gold" with Purdy.

"It’s kind of easy to say you can plug in quarterbacks, and they would all be winners as well just because there’s so many weapons around them. But that’s how you win championships, man," Gronkowski told Fox News Digital in a recent interview.

Brock Purdy celebrates a first down

Brock Purdy of the San Francisco 49ers reacts after running for a first down in the fourth quarter against the Pittsburgh Steelers at Acrisure Stadium Sept. 10, 2023, in Pittsburgh.  (Joe Sargent/Getty Images)

"Everyone has to be clicking. The quarterback has to be clicking, the wideouts have to be clicking, the defense has to be clicking, the organization as a whole has to be clicking. And that’s what they’re doing, and that’s where Brock Purdy fits. 

"He fits great with that organization, he fits great with that team. So you can’t say that. It’s easy to say you plug in any quarterback, but (realize) that’s not the case. Brock Purdy is the man in San Francisco. He understands the organization, his character fits in perfectly, and they definitely hit the gold with him being on his rookie contract making only, like $800,000, which is wild."

Brock Purdy before a game

Brock Purdy with his hand over his heart (Getty Images)

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The only game Purdy has lost in his career so far was the NFC championship game against the Philadelphia Eagles last year when he had to leave the game after tearing the UCL in his throwing elbow.

This season, Purdy's 123.1 passer rating ranks atop the NFL, and his 72.1 completion percentage is second behind Josh Allen. Purdy's on pace for 4,321 yards, 30 touchdowns and 17 wins.