The armies of the first crusade are defeated by the Seljuks at Dorylaeum in Asia Minor.
Yes? Was this a question or merely a delusion?
Oh, alright. I suppose if I say nothing more, I'll be reported for trolling or somesuch silliness.
Turks win, the Crusaders are delayed into the winter or the following year. It takes a long time to cross Anatolia and the crossing could be worse. They arrive at Antioch harried and humbled. The siege does not go their way. Byzantine rule isn't revitalized in the short term, and the Crusading cause takes a hit. Perhaps they find a (more) naval route, or another battle against the Turks defeats them. Either way, there's a delay and a series of butterflies that could spell doom for the Crusade. And if the First fails, who knows if there will even be others.