Any European nation, Austria and Russia in particular, could've easily taken the Ottoman Empire in the late stages of its empire. They didn't adopt the use of the iron clads, their canons were bulky and not fit for open field battle as their European counterparts, and were to detatched from Europe to modernize. Nations started to break away and nations that did modernize their army, such as Muhammed Ali Pahsa modernizing his army, were at the gates of Constantinople and had not the European powers intervened there would not have been an Ottoman Empire.
As Russia set to invade to Ottomans, Britain, France, and Austria had to help the Ottomans in order for them not conquer the Ottomans and grow to strong. The only reason the Ottoman Empire didn't die out before the 1900s is because of European intervention in the matter.