The San Francisco 49ers made what could be the biggest move of the NFL offseason Thursday, signing quarterback Jimmy Garoppolo to a five-year contract.

The deal is worth $137.5 million, a source told Mike Garafolo of NFL Network.

That figure would make Garoppolo the highest-paid player in NFL history in terms of average annual value, according to Garafolo, surpassing Detroit Lions quarterback Matt Stafford, who signed a five-year, $135-million extension last August.

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The 26-year-old blossomed after being traded from the New England Patriots in 2017, leading the 49ers to victories in each of his five starts to finish the season. Over that stretch, he completed more than 67 percent of his passes for 1,560 yards and seven touchdowns.