He made heavy contact with the wall and his car nearly flipped over before coming to a rest.
Tost showed some support for the Kiwi saying he wasn't to blame for his incidents during the season.
"For example, we had the crash of Hartley with Stroll in Canada and his heavy blow during the free practice at Silverstone due to a suspension problem, and in Monza he was still hit by Stoffel Vandoorne and Marcus Ericsson, which was not really good."
Gasly's biggest crash came at the Spanish Grand Prix when his car was taken out by Romain Grosjean.
The team finished ninth in the constructors championship with 33 points across the 21 races, which included 10 retirements.
One low for the team came at the Chinese Grand Prix when Gasly crashed into the Kiwi, damaging Hartley's front wing.
"I think the accident with Pierre was down to a miscommunication," Hartley said at the time.
Hartley was dropped for Toro Rosso for next season, replaced by Thai driver Alexander Albon. He has reportedly been linked to racing for Porsche in Formula E.
In an interview with Newstalk ZB's Mike Hosking last month, Hartley suggested there was more to his sacking than on-track performance.
"I would love to tell the story one day," he told Mike Hosking.
"The politics I don't enjoy. It took me some time to get used to the extra media attention. What I will say is Formula One is very complicated, there's a lot of money involved, politics and some of the reasons why drivers stay or leave isn't always in your control or of reasons for pure performance.
"In any case, I left the paddock with my head held high. I knew I'd given it my best shot this year. I knew that I'd stepped up to the plate when I needed to."