A lot of men will dessert, some may pass to the royalist cause, Blanco Encalada would probably get command of the army and they will call for Carrera to help. Maipú is just unwinnable without San Martín, but I'm not sure if the battle will even be fought, I'd say it will, this time the royalist won't just accept to exile most of the leaders of the independence; there's the possibility of them refusing to give battle, so siege of Santiago, I guess; the odds against the patriots are overwhelming, and morale would be in an all time low, they may be able to achieve a pyrrhic victory, but I think it's unlikely. Most of the leaders will be executed, others imprisoned, those who had escaped to Mendoza beforehand will survive. The royalist are probably able to take the rest of Chile by early 1819.
Carrera has another chance in 1820 or 21, thanks to Riego's coup, he could probably get those who escaped to Argentina on his side and Mapuche tribes; the royalist would probably do a lot of horrible things, so I don't think they will be liked. I'd say Chile is once again liberated, at least most of it, but in the meantime a lot of things would have changed. Cochrane won't be there, and I wonder what he would do, honestly, maybe with Bolivar or something; so Spain has naval supremacy and has had time to consolidate it. That means an operation into Peru is almost impossible. I'd say that Carrera and Bolívar are just enough to overwhelm the royalist enough to allow the capture of Ecuador. Ecuador falls and Bolivar will be engaged in a long war against the royalist.
It could result in many things, and Chile could start being bigger than OTL, but things for Chile are actually pretty bad. Instead of having a good foundation Chile has lost most of the leaders of its independence and instead it has a caudillo, which will lead to Chile being much more unstable and having a series of dictatorships. Bolivar and the royalist will engage in a long war, in which neither side will be able to break the other, so the war would turn out to be about territory instead of independence. The royalist will have an state based of Peru and Bolivia, which will only titularly be a viceroyalty or someone will be named monarch, the viceroy or some general.
