49ers sign linebacker David Mayo

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The 49ers continued a busy day of stacking up depth on defense.

The team announced the addition of Panthers linebacker David Mayo.

A former fifth-round pick from Texas State, Mayo played in 59 games and started four for the Panthers, filling in capably and creating a niche on special teams.

He arrives on the same day they signed cornerback Jason Verrett and brought back safety Antone Exum, following their trade for pass-rusher Dee Ford and the signing of linebacker Kwon Alexander.