49ers QB Brock Purdy is almost done with the NFL’s concussion protocol

San Francisco 49ers quarterback Brock Purdy seems to be recovering from his apparent concussion at a remarkable rate.

Purdy began experiencing concussion symptoms on the flight back from Minnesota after San Francisco’s 22-17 loss on Monday night, head coach Kyle Shanahan told reporters Wednesday. He was tested Tuesday and officially placed in concussion protocol after that, Shanahan said, leaving just four days before the 49ers’ next game, against the Bengals on Sunday.

Shanahan told reporters Wednesday that he believed the 23-year-old quarterback had enough time to clear protocol in time to take snaps Sunday. So far he’s been proven correct. Purdy’s participation at practice Thursday indicates that he is in Phase 4 of the NFL’s five-phase Return-to-Participation protocol regarding concussion injuries. Being 80% done with the protocol means participating in “club-based non-contact training drills,” according to the league.

“The player continues cardiovascular, strength and balance training, team-based sports-specific exercise, and participates in non-contact football activities (e.g. throwing, catching, running and other position-specific activities),” the description reads. “Neurocognitive and balance testing should be completed no later than the end of Phase Four with the results interpreted as back to baseline.”

This would imply Purdy went through the first three phases of the return protocol in about 24 hours. That includes prescribed rest with limited activities (Phase 1), supervised aerobic exercise (Phase 2) and exercises that “mimic sport-specific activities” (Phase 3). All that apparently remains now for Purdy is clearance from a team physician and a return to contact drills. He’ll also need an exam from an independent neurologist to officially approve his return.

The NFL notes that there is no set time frame for return to participation — meaning that according to its own system, there’s nothing necessarily amiss with Purdy’s near completion of the protocol in about a day. So, either the concussion protocol is so foolproof the league can confidently say a player is all better in just a few days, or so flimsy a savvy player could easily game it to complete it quickly, regardless of what their actual health status might be.