49ers' 4-0 start hides a rift: Brock Purdy's mechanics quietly under fire

The San Francisco 49ers are 4-0 for the third time since 2019 and the seventh time in franchise history, but the conversation inside the building isn't about the record.

Brock Purdy completed 19 of 30 passes for 218 yards and 2 touchdowns with a 107.4 passer rating in Sunday's 24-14 win over the Denver Broncos at Levi's Stadium. He also tied his career high with 10 carries for 29 yards. It was his fourth straight game with at least 2 touchdown passes and a passer rating of 100.0 or higher.

The numbers look like a quarterback playing the best football of his career. The film tells a more complicated story.

Purdy's mechanics — his footwork, his base, the timing of his release — have quietly become a point of discussion among people who study the position. The concern isn't the production. It's whether the production is sustainable.