Brennen (elbow) agreed to a one-year, major-league contract with the Giants on Sunday, Justice delos Santos of The San Jose Mercury News reports.
The 28-year-old was limited to 159 plate appearances between Triple-A and the majors last season with the Guardians, as he underwent Tommy John surgery in June and then required sports hernia surgery in September. A healthy Brennan should serve as a fourth outfielder for the Giants.