Hamilton won that very Grand Prix in Brazil after the infamous Ocon-Verstappen clash took place but was apparently driving on fumes when it came to the actual power unit. Failure even looked imminent at some point, but some adjustments from Hamilton inside the cockpit combined with some setting changes back that were made during the race back in Brixworth helped get the five-time champ over the line.
Mercedes could either opt to install some new elements in Hamilton's W09, which would mean that he would take a grid penalty in the last Grand Prix of the season next week, or the Germans could use an old engine again, with the risk of potential failure attached to it.
"If we just go back a little bit and look at what happened in the race, after the first pit stop with Lewis we noticed quite a significant problem, which required a huge amount of input from a number of sources," Mercedes strategist James Vowles said on Mercedes' YouTube series Pure Pitwall.
"We have a team back in the UK at Brixworth who work alongside us on the intercom, and we have a huge team trackside working together diligently to understand what we can change on the engine to get to the end of the race.
"They did a fantastic job. It wasn't one change, it was a huge number of changes across a 40-50 lap period, where they were working with Lewis to adjust various componentry and get that power unit to the end of the race. They did a fantastic job.
"The net result of that, though, is that the engine has sustained some level of damage, but we don't yet understand what. It has to be inspected and understood before we can make any decision going forward to Abu Dhabi."
Hamilton has of course already wrapped up the drivers' title earlier this year in Mexico, and Mercedes secured their fifth consecutive constructors' championship in Brazil last weekend. Either way, a grid penalty wouldn't be the end of the world.