At Manzikert the Turks made an impact, so much so that the 10s of 1000s of mercenaries in the Emperor’s employ deserted the field when they saw (or feared) the destruction of the Varangians at the core of the Byzantine army.
The Romans aka Byzantines were pursing the Turks who were retreating and not giving battle. The Romans lost track of time in heat of pursuit and night fell and became separated form each other and the Turks using Mongol tactics ambushed them.
In fact by all accounts the Turks did not even know they had wiped out the only field army the Byzantines had in the region. They captured the emperor and made ransom terms like a normal raid party kind of thing. Only many weeks later when no Roman army appeared in the field did the Seljuks raid deep and established the the Seljuk Rum territory in a depopulated Anatolian heartland.