Brady Henderson of ESPN Seattle confirmed Garafolo's report.
According to Garafolo, the NFL will issue no additional punishment to the Seahawks, but the infraction will factor into any future violations.
In January, Seahawks head coach Pete Carroll said Sherman had played the second half of the season while carrying an MCL injury—a fact the team hadn't announced until after its loss to the Atlanta Falcons in the NFC Divisional Round—per ESPN.com's Sheil Kapadia.
The NFL's official rules stipulate teams are required to inform the league, opponents, media and broadcast partners of any player injuries on a weekly basis.
ESPN's Chris Mortensen reported in January Seattle faced the loss of a second-round draft pick as a worst-case scenario from the violation.
Garafolo noted the Seahawks successfully argued they misinterpreted the rules regarding the reporting of injuries since Sherman practiced despite the injury.
Pro Football Talk's Mike Florio poked holes in that line of reasoning, though: "Here's the first problem with that excuse for not issuing punishment: Sherman at times did miss practice, with the designation that the absence wasn't injury related. For example, he didn't practice the Thursday before the divisional-round loss to the Falcons.
"Sherman also didn't practice on the Thursday before the wild-card win over the Lions. He also didn't practice on the Thursday before the Week 16 game against the Cardinals."
The NFL's ruling on the Seahawks will likely be good news for the Pittsburgh Steelers, who encountered a similar situation with running back Le'Veon Bell. ESPN's Adam Schefter reported the league began investigating whether the Steelers ran afoul of the injury report rules following their AFC Championship Game defeat to the New England Patriots.
Head coach Mike Tomlin said after the game Bell had been dealing with a groin injury heading into the game, per the Tribune-Review's Chris Adamski. Like Sherman, Bell missed three practices in the two weeks before the conference title game, with the Steelers' injury report listing his absence as "not injury related."