Not necessarily. Attrition due to the need to fight more battles could mean reinforcements are a necessity so that successes are reinforced.
How many troops were in reserve during the rhenish and italian campaigns?
And even if more troops are recalled from Napoleon's army, the guy could still deal quite a bunch of damage, even if he'll be unable to march directly over austrian territory from Venetia.
Or, a more successful rhenish campaign would even benefit Napoleon -- with the austrian army distracted in south Germany, Napoleon could advance from Venetia and take the austrians by surprise.