Listen to this article
The Spaniard was running second when he was tagged by Kenan Sofuoglu and sent into a violent accident, during which Sofuoglu's bike clipped Simon as they went into the gravel.
Simon was able to stand up and lean on the barrier afterwards but was in clear discomfort.
After an initial examination at the circuit's medical centre, the Aspar rider is set to be transferred to a Madrid hospital for surgery.
Moto2: Bradl scores another Moto2 victory
Moto2: No penalty for Sofuoglu over clash