A 6-3 6-2 triumph for Djokovic in just 68 minutes on Wednesday moved him into the semi-finals with a match to spare.
Djokovic will face alternate Cameron Norrie on Saturday (AEDT) already knowing he will finish top of the Green Group after straight-sets wins over Casper Ruud and Rublev this week.
The Serbian dropped serve in the first game of the match against world number five Rublev but had few problems from then on.
Victory took Djokovic to 50 wins on the ATP Tour this season. He has been beaten just six times in 2021 and is now two victories away from a record-equalling sixth ATP Finals success.
The 34-year-old has won 12 of his 13 matches since the start of the US Open, losing only to Daniil Medvedev – his main rival for glory again here – in the final of that competition.
"It was a great performance overall," said Djokovic, who won 27 of 31 points on his first serve and had 14 aces to zero double faults.
"I served well and that helped tremendously. I wanted to put him out of his comfort zone, taking away the time and mix up the pace.
"I knew that I had to be on my toes and start well.
"I dropped my serve again like in the first match against Ruud. It was quite a nervous start from both of us until 4-3, then with new balls I somehow managed to find the right shots at the right time.
"I made him play. Winning the first set I put additional pressure on him, and I started to maybe play more consistently from the back of the court."
Rather than 2019 winner Stefanos Tsitsipas, who has withdrawn with an elbow injury, Briton Norrie is up next for the world number one at the ATP Finals.
"I always like playing new players, particularly in one of the greatest tournaments in the world here in Turin," added Djokovic.
"Cameron deserves to be here, it is not lucky. He worked his way to Turin with great wins in Indian Wells and some other tournaments.
"So it will be fun to watch him play against Ruud and I will get ready for my next match."
Djokovic has now made the last four of the ATP Finals on 10 occasions, with this being his 40th career win in the tournament (16 defeats).