Ugh. I don't know how it's even possible. Look, victories like Neva are COMPLETELY impossible in this game. The battles are all about the numbers, and the Russians never seem to run out of men, no matter how many of them I kill. They'll lose a quarter of their army while I'll lose almost nothing and I'll still lose. I'm not running low on manpower, but I can't afford a 100k man army as Sweden. I managed to WP Poland but Russia is utterly unstoppable. Their armies run like cowards when chased by a superior force, like all AI armies, leading me to have to run all around through Russia trying to destroy them. Has anyone done it? If so, how?
Well, I've never been in your situation, but I will tell that it's not a good idea to chase Russia's armies into their land, especially if it's winter! What exactly are you trying to achieve? You'd need to give more details for a more helpful response.
If you were trying to take Neva, what I would do, (I believe there are two adjacent provinces that belong to Sweden de facto?), is land an army in Neva, as large as you can field without going over the supply limit, and then do the same with the provinces behind Neva. If they try to attack your besieging army you can simply toss-in the bystanders, and if you're Quality, I assume, than it would be likely for you to win. Once you have Neva, if you have money and spies, I would support revolts all over Russia, and naturally, their armies would divulge and eventually deal with the rebels, giving you headway to go a little deeper, and take the provinces adjacent to Neva, with the same system of guarding your besieging armies from behind.
I would never, ever, fight a war of attrition with them, though. Since in most cases it would take nearly a month to go from province to province, leaving you succumb to serious attrition casualties, and their morale would never break.