Since Viggo specifically arranged for him to be the last one to arrive at the forest outside the city and didn't inform him that Trager and Raider would also be there, it was clear that Viggo did not trust him. Viggo wanted Trager and Raider to monitor Aizen's every move after encountering Georgie and Nero.
However, Viggo also deliberately sent Raider to the forest first, and in the end, it was Raider's sudden appearance that allowed Aizen to kill Trager immediately.
This clearly showed that Trager didn't know Raider was hiding in the forest.
From this, it could also be deduced that Viggo didn't trust Trager either. Arranging for Raider to remain hidden was to have him monitor both Trager and Aizen.
This was essentially a classic "mantis stalks the cicada, unaware of the oriole behind" scenario.
Aizen was the cicada that revealed itself first, successfully drawing out Trager, the mantis, to attack him.