Vesnina, Mladenovic in Indian Wells semis
Vesnina staved off six break points in the last game, falling behind 40-love to start, before closing out the 71-minute match with two forehand winners. She then clinched her spot in the finals by serving out her final game.
"I was hitting a lot of unforced errors", she said. Little, lazy mistakes for me. "If I go out there and play the right tennis and play the right strategy, I can give myself a shot".
The 14th-seeded Russian takes on No. 28 seed Kristina Mladenovic in the semifinals.
Mladenovic, the 28th seed, continued an impressive run of form beating 13th seed and 2011 victor Wozniacki 3-6 7-6 (4) 6-2 to reach her first Premier Mandatory semi-final and guarantee her debut in the Top 20 in next week's WTA rankings.
No. 3 Karolina Pliskova and No. 8 Svetlana Kuznetsova are set for the other semifinal.
Vesnina, a victor over world number one Angelique Kerber en route to the final, went 4-2 up in the first set courtesy of a fizzing backhand at the feet of the eighth seed, who netted.
Down a set and three service breaks at 5-1 in the second set, Mladenovic won three straight games - fending off one match point - before Vesnina held serve for the victory. After the match Williams acknowledged some physical "issues" that had troubled her throughout the tournament, although she declined to elaborate. She has Sjogren's syndrome, an autoimmune disorder.
The win marked the biggest title of Vesnina's career and she collapsed to the court with a mixture of ecstasy and exhaustion at the end. "I had some issues".
"'Kiki' is having a great season, she is on fire, so I was trying to focus point-by-point". "So finally, this year, after all these years, I'm in the final".
The eighth seed's luck ran out as Vesnina stepped into the court and ripped a return down the line breaking for 5-4.
Nishikori had not dropped a set in the tournament until losing the first against Sock.
After a dramatic game, Wawrinka managed to eliminate Dominic Thiem from Austria with 2-1 in sets, 6-4 4-6 7-6.
The duo have met on two previous occasions on the WTA Tour, with Kuznetsova winning the most recent encounter, a straight sets triumph in the semi-finals of the WTA Estoril in 2014. "I hope I can enjoy it and hope I can show the best tennis as well in the final". "I didn't hold when I had the opportunity and all of sudden those games kind of slipped away". "It was a very important match for me".