Finn Bottas, who topped both First and Second Practice for Mercedes at Silverstone on Friday was handed the penalty after the team were left with no choice but to replace the unit which had done four of the six races it was supposed to.
FIA rules dictate that a gearbox must last six consecutive events, but if a driver does not finish a race, they are allowed to fit a fresh unit for their next event.
Seeing as the 28-year-old took his second victory in F1 in Austria on Sunday, he was not entitled to take a fresh gearbox for Silverstone.
That unit had done Monaco, Canada, Azerbaijan and Austria, before Mercedes noted a similiar issue with the gearbox on team-mate Lewis Hamilton's car, which led to his five place demotion in Austria last time out.
At best, Bottas will start the race in sixth place, with the ideal result for Mercedes in qualifying being Bottas being fastest and Hamilton second so the British driver inherits Pole Position, as opposed to Ferrari's championship leader, Sebastian Vettel.
It won't happen again
Mercedes are confident that they have solved the issue which struck Hamilton and now Bottas, which should keep penalties to a minimum.
While the Silver cars have a 33 point advantage over the Red ones in the constructors', it hasn't been all plain sailing for Ferrari.
Both Vettel and Kimi Raikkonen have used more engine components than Hamilton or Bottas, which could harm the Italian manufacturer during the championship run-in.