Russia has ~144 million people. They can scrape together impressive numbers of manpower, but it's a whole another matter what they're going to fight with and how effective those poorly (if at all) trained troops really are. We've already seen AK-variants rusted so badly that they're mostly danger to the one pulling the trigger and bolt action rifles. Of course that amount of soldiers, no matter how poorly equipped, does pose a threat, but at the big picture (from my armchair general position) the bigger question is how long Russia can keep up with their artillery. And with 4,5k destroyed they're running low, but there's still considerable amount of equipment left.