A coupler assembly includes a valve with a locking ball locking mechanism and a locking sleeve interacting with the locking balls to lock the valve in the connected position. A slider is positioned radially between the ball body and the locking sleeve, and longitudinally inward relative to the locking balls. During a connection operation to a nipple, the slider is moveable along the ball body to permit movement of the locking balls into an inner recess defined by the locking sleeve as the valve moves toward the connected position. The slider is biased to return to the first slider position. During a disconnection operation, the locking sleeve is moved to a second sleeve position. As the nipple moves longitudinally outward, a surface of a locking shoulder of the nipple moves the locking balls into an outer recess of the locking sleeve to permit removal of the nipple.