The 49ers had a prime opportunity to take a two-score lead.
San Francisco, though, did nothing with the good field position.
On third down, Purdy was forced out of the pocket and scrambled for 4 yards.
The 49ers punted on fourth-and-11 and Mitch Wishnowsky's punt has pinned the Chiefs at the 2.
The 49ers still lead 10-3.