Gilles Simon staged a dramatic comeback to knock out top seed Marin Cilic and set up the title clash with second seed Kevin Anderson, who prevailed in an excruciating battle against a spirited Benoit Paire at Tata Open Maharashtra in Pune on Friday.
In a sensational turnaround, the unseeded Frenchman toppled the world number six from Croatia 1-6 6-3 6-2 in a gripping semifinal.
He had also sent packing third seed and defending champion Roberto Bautista Agut in the second round.
Simon, who was once a top-10 player but now placed a humble 89th, shrugged off opening set debacle to stun Cilic, the 2017 Wimbledon finalist, in one hour and 51 minutes.
He will now gun for his 13th ATP title, having played his last final in September 2015 when he lost to compatriot Jo- Wilfred Tsonga at home in Metz.
Anderson, the US Open finalist, rallied to edge out Paire 6-7(6) 7-6(2) 6-1 in two hours and 19 minutes.
Paire struggled with cramps in his right leg in the deciding set and Anderson, who fired 26 aces, pulled away with an easy break of serve.
Paire got the crowd involved with him, several time gesturing towards fans to cheer for him.
Cilic, with an intimidating 66 frame, was ruthless in the beginning but Simon, using his wealth of experience, effortlessly changed the complexion of the game.
Simon's consistent returns, even on the powerful serves of Cilic, unsettled the Croat, who started to make unforced errors and could never recover.
He was controlling the match with his powerful serve but started to struggle in putting his first serve in, which cost him as the match progressed.
Simon came to the match with a superior 4-1 head-to-head record against Cilic and improved it further. They last played in 2016 at the Miami Masters, where Simon won in a three- setter.
"The balls were not as penetrating as it was in the first set and he had more time to play. My first serve did not come when I needed and there was no rhythm in the shots during rally," Cilic said.
"He is a counter puncher but I came into the match with good mind set. He was returning very well. He tried to play long rallies. His ranking may be low but he knows how to play tennis," Cilic said but added that he was overall satisfied with the level of his game.
Simon endured a tough 2017 season during which he struggled to reach even quarterfinals on Tour and his ranking plummeted to 89 from 24 at the beginning of the year.
Once ranked world number six, Simon struggled to find his rhythm as his ground strokes were all over the place in the opening set.
Cilic, as usual, began in an explosive manner firing aces and service winners while Simon struggled to win points on his own serve.
The Frenchman dropped serve at love in the second game and won only two points in the first three games of the match, underlining the dominant start the Croat made.
After being broken at love, Simon saved two break points in the fourth game but netted a backhand on the third while Cilic held his own to race to a commanding 5-0 lead.
Egged on by the crowd and aided by Cilic's unforced errors, Simon got on board by holding his serve in the sixth game in which he saved two set points.
Cilic though remained ruthless and began serving for the set with an 226km ace and closed it with another on his fourth set point.
In a complete turn around, Simon started to return better in the second set.
The Frenchman began to hold his serve and broke Cilic in the second game to take a 3-0 lead in the second set. The break happened in a bizarre manner. At 30-30, Simon found a surprise service return winner as Cilic left the ball, thinking it's going out.
On the break point, the Croat netted a backhand. Simon broke Cilic again when his rival hit a backhand long on the second break point and found himself leading 4-0.
With momentum on his side, Simon began to dominate rallies as he stunned Cilic with some amazing winners and served out the set in the ninth game.
With balls becoming heavier after some hits, Simon mixed it up nicely, sending some short and some deep returns to engage Cilic in long rallies, enticing errors from him.
From 40-15, Cilic lost his serve in the opening game of the decider.
The next game was an engrossing battle with Simon fighting off two breakpoints after four deuces for a hold. Cilic had no clue how to cope with Simon's returns.
The Croat dropped serve at love in the seventh game and Simon served out the match on Cilic's backhand error on second match point.