The wide receiver made his debut for the AFC West side last season, and is pushing for a greater role with the team in 2014.
The quarterback told CSN Bay Area: "He's a long strider, a big guy who can stretch the field vertically and go up and get the football.
"Obviously, his height and his ability to adjust in the air are some of his strengths, as well as some of the intermediate routes.
"Just being able to get to the top of his route, come strong out of his cut, he can be a guy that can stretch the field for us."
Holmes had 431 receiving yards and a touchdown in 10 games with the Raiders last year.