They have more than enough personnel, logistics & equipment to roll up Ukraine as a whole in 2-3 weeks, but they don;t have the money or desire to occupy the country. That's why I think if (and with diplomacy planned for all next week, it is still a big if) they invade it will be a Georgia type story- surround Kiev, completely destroy the Ukrainian armed forces, and then accept peace in return for Donetsk, Lugansk and a corridor to the Crimea.
But I still feel this is at the outer edges of possibility- the blowback from such an attack could be catastrophoic internationally and consequences unpredictable internally.
He has the world's attention, divided NATO, and has his felt boot on the throat of the Ukrainian economy, without committing a single soldier. If it's enough to get Ukraine to observe the Minsk agreement and perhaps concede a little more, then it's been a spectacular success. Much harder to physically fight your way to any such gains.