The good news for Gasly, however, is that the fresh unit is understood to be the new-spec Honda engine, as used by team mate Brendon Hartley in qualifying.
Gasly hit problems with his own newly-upgraded power unit in final practice on Saturday, prompting Toro Rosso to swap it out for a previously-used, older-spec engine ahead of qualifying.
Down on outright power relative to Hartley as a result, Gasly could only qualify 16th to the New Zealander’s 12th.
Given that lowly grid slot, and the team’s upcoming power unit allocation plans, Toro Rosso then decided to make yet another change, moving Gasly on to his fourth engine of the season, as well as changing other power unit elements.
With teams only allowed to use three engines per season, the resulting penalty drops him to the back row of the grid in 19th place, alongside Romain Grosjean who failed to set a qualifying time for Haas.