Turkey is fairly easy to play in an alliance with Russia (the "juggernaut"). The two of them partition the Balkans and Austria-Hungary, possibly with the help of Italy. Then they go their separate ways with Russia fighting Germany and/or England, while an enlarged Turkey crushes Italy. They need to come to an agreement about the Black Sea, but as long as Turkey builds mainly fleets and Russia mainly armies, they're fine.
A problem seems to arise if Turkey allies with say, Austria-Hungary against Russia. Turkey can get control of the Black Sea and Sevastopol (maybe Rumania). But it needs fleets to cover these areas, and its navy seems to be stretched out between these areas and the Mediterranean. If it tries to move north, it will likely be "capped by whoever (Germany or Britain) has captured Moscow.
Turkey's next natural target seems to be Italy (another naval power), except that it is vulnerable to a counterblow by land from Austria-Hungary in the Balkans. And if Austria-Hungary builds mainly armies, the combined Turkish and Italian land forces might have difficulty reconquering the Balkans even if they were allied.
So how would Turkey avoid getting "boxed in," absent an alliance with Russia?