49ers ink CB Brock to extension

Santa Clara, CA ( - The San Francisco 49ers signed cornerback Tramaine Brock to a four-year contract extension that will run through the 2017 season, the team announced Friday.

Financial terms were not disclosed by the 49ers, though Comcast SportsNet Bay Area reported the deal to be worth $16 million with $7 million in guaranteed money.

Brock, who had been scheduled to hit unrestricted free agency at season's end, has emerged as a key defensive contributor for San Francisco in 2013 after mainly being used on special teams over his first three years. The 25-year-old leads the 49ers with four interceptions, one of which he returned for a touchdown, and has compiled 18 tackles and nine passes defensed while supplanting since-released veteran Nnamdi Asomugha as the team's primary nickel back.

"Tramaine is a great example of what hard work and dedication can lead to," said 49ers general manager Trent Baalke. "He has taken advantage of his opportunities since signing with our team as an undrafted free agent in 2010 and has certainly earned this extension."

Brock also led the 49ers with 15 tackles on special teams during last season's run to an appearance in Super Bowl XLVII.