Rublev had come to London in good form with three titles in his last five tournaments, but began Thursday’s match knowing his season was effectively over having lost previous group games to Rafael Nadal and Stefanos Tsitsipas.
That knowledge appeared to give the 23-year-old Russian back the freedom in his game and he raced to a comfortable 6-2, 7-5 victory over Thiem, who had already guaranteed top spot in his group.
The defeat cost the US Open champion a further 200 points in the ATP rankings, a 300th career win on Tour and £115,000 for winning all three group games.
But the Austrian knows he can brush aside the defeat as a one-off having produced one of his best performances of 2020 to beat Nadal just 48 hours earlier.
Rublev raced into a 4-0 lead before Thiem finally held serve and rounded off the set with 11 winners and not a single unforced error in a seemingly faultless set.
Thiem looked steadier to hold at the start of the second set, but it was only a temporary reprieve as Rublev broke his next service game.
He looked to be cruising to the win only to be broken when serving for the match at 5-4. But Rublev immediately broke back to serve out the match at the second attempt.
Afterwards Rublev said: “I started really well. I think Dominic didn’t start that well and I took advantage and that helped me to have more confidence and play better and better. I think Dominic already focused for the semi-finals. I wish him the best of luck. He deserves to win the title.”