49ers head coach Kyle Shanahan made a big revelation involving the health of Nick Bosa.

The San Francisco 49ers and Kyle Shanahan watched the Seattle Seahawks take advantage of a defense missing Nick Bosa. Seattle snatched the lead with 12 seconds left off Geno Smith’s 13-yard touchdown scramble to win 20-17.

Smith and the Seahawks pulled out the last-second victory with Bosa sidelined with an injury. Many who watched the game believed the All-Pro pass rusher aggravated his previous hip injury. But turns out, Bosa has a new ailment per Shanahan.

Shanahan revealed via NBC Sports Pro Football Talk that Bosa injured his oblique during the third quarter. Bosa limped off and never returned to the game.

Bosa managed to grab one sack of Smith. He delivered four tackles, two solo stops and nailed two ball carriers behind the line of scrimmage. Bosa also pounded two QB hits of the Seahawks’ QB1.

But when Bosa left, Seattle clearly took advantage. One insider shared a revealing stat that impacted the game after Bosa’s departure.

How 49ers struggled vs. Seahawks after Nick Bosa left

Bosa changes the complexion of opposing offenses off his presence alone. Teams opt to steer away from running to Bosa’s side or use an extra blocker to slow his pass rushing pursuits.

The Seahawks, however, witnessed a spike in their average yards per play once Bosa left. ESPN 49ers insider Nick Wagoner presented this revealing stat from the 49ers loss.

Seahawks with Nick Bosa on the field Sunday: 3.3 yards per play

Seahawks with Bosa off the field: 6.1 yards per play

— Nick Wagoner (@nwagoner) November 18, 2024

Wagoner added an even more concerning report for 49er fans in a postgame conversation with Bosa.

“Asked his concern level that he might need to miss time, Bosa said ‘It’s definitely there,’” Wagoner shared on his X (formerly known as Twitter) account.

One more 49ers insider in San Francisco Standard reporter David Lombardi noticed the effect Bosa’s injury had on the Niners.

“Seattle didn’t score a TD until Bosa was off the field. His injury essentially made a more competent offensive performance mandatory for the 49ers. They didn’t deliver it,” Lombardi posted on X.

The 49ers’ season appears to have fallen off the tracks. The defending NFC champions are losing ground in the race for the conference’s top seed. And with an even record, the Niners are still a game behind the current NFC West leader the Arizona Cardinals.

Bosa is dealing with both a new injury, plus new struggles inside the 49ers’ facility. However, he hasn’t wavered from his confidence.

“We have a lot of games left. All we gotta do is get in the dance. I definitely still have confidence,” he said via KNBR postgame.

Bosa’s status for next Sunday is now too be determined. San Francisco has a crucial November road battle against the 7-3 Green Bay Packers, who won off a blocked field goal in the closing seconds against the Chicago Bears.