Back in March in the last 32 at the Indian Wells Masters, Dimitrov had the same number of chances to win but squandered them all as the American roared back to claim the spoils in a final set tiebreak.
A similar recovery threatened as the Bulgarian served at 5-3 up in the decider.
Dimitrov had two. And lost them. He then had to save a break point before gaining his third match point. That too was fluffed. A second break point also had to be fought off.
The fourth match point yielded dividends after one hour and 58 minutes. It finished 4-6 6-0 6-3.
Sock was munificent in defeat. “I thought he stepped up his level in the second and third sets. He came up with some pretty crazy shots in the third set at inopportune moments for myself.
“Grigor has stepped up his overall level, that’s for sure. That’s the reason he has been playing so consistently all year. That’s why he is in the final.”
Dimitrov will play fellow tournament debutant David Goffin in Sunday’s showdown.
The pair met in their second match in the round robin stage on 15 November. Dimitrov annihilated the Belgian 6-0 6-2. But that tie followed Goffin’s first win over Rafael Nadal.
The final at the 02 Arena will come a day after Goffin’s first victory over Roger Federer.
The triumph enabled him to join a pack of six men who have overcome the two titans in the same tournament. If Goffin embraces the otherworldly, then superstition might fortify his endeavour: Novak Djokovic was the last man to achieve the feat on his way to the crown at the 2015 ATP Finals.
Dimitrov though will be buoyant. His second win in four meetings with Sock catapulted him to third in the rankings – his highest position in his nine years on the tour.
“It is a wonderful reward,” said Dimitrov. “This is what I have been working for. It is not only good for me, it is good for the whole team. It gives us a good platform to start in the off-season and to have a good start for next year."
He added: "As for the final, it is another match for me and it's a different stage for both of us and it will be a wonderful occasion for both of us."