Actually, it's Putin who cannot win. Even if he threw everything he had and managed to occupy a country of 44 million people, second largest in Europe by landmass - he wouldn't be able to hold it. That would require the kind of resources he doesn't have. Also the minute he withdraws, which is just a matter of time, ukrainians will kill his puppet government and take their country back. So yeah, Ukraine will suffer major losses, but ultimately time is on their side.