Holding onto the staff, Quinn thought the best thing to do was to take it out of the Monkey god slayer's hand. If he was to treat it like a weapon, it had an incredibly dangerous active ability, being able to change its size like so, yet also being able to keep the same amount of force.
In Quinn's mind, it made it quite clear that although the shape of the weapon would change, the weight of the weapon always stayed the same. It also explained the Monkey man's great strength as well. Because he was able to swing it around so effortlessly.
At first, grabbing onto the staff, Quinn was using his extreme strength with the 1st stage of Qi to power himself and pull the weapon out of his opponent's hand, but it didn't seem to be enough, as the other held onto it tight.