The San Francisco 49ers have successfully locked up one of their core defensive players.

Linebacker NaVorro Bowman agreed to a five-year contract extension, the team just announced. Adam Schefter of ESPN broke the story, reporting earlier Bowman was close to signing a five-year extension, a deal that will keep him in place through the 2018 season.

The 49ers signed Patrick Willis to a $53.5 million, seven-year deal in 2010, a contract that included $29 million guaranteed. It’s unknown how big the windfall will be for Bowman, who pairs with Willis to give the 49ers one of the best tandems at the position in the NFL.

Bowman is in the third year of his rookie contract and is earning $540,000 this season. He was scheduled to earn $575,000 next season and he will be earning much, much more than that.

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Brad Biggs covers the Bears for the Chicago Tribune