The Frenchman scored points in his first race since demotion at Belgium and was unfortunate to get tangled up in the Vettel-Stroll incident at Monza, going on to finish 11th.
Tost is well aware that Gasly's confidence will be fragile, but is sure that he can rediscover his best form back at Faenza.
"If a driver is coming back from Red Bull to Toro Rosso he is shocked and demotivated and he's lost confidence," said Tost.
"The job from the team and from my side is to help them, support them and to bring together all the ingredients they need to perform as well as they did beforehand. Because Red Bull Racing took them when they were successful with us.
"He came to the factory as if it was yesterday.
"From the beginning onwards there was good cooperation, we trust each other, we support each other. I am convinced that he will soon have back his confidence."
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