In the fourth quarterfinal, 13th-seeded Julia Goerges of Germany faced former French Open semifinalist Kiki Bertens, with both players having reached the last eight at Wimbledon for the first time.
Rebounding from her shock first-round elimination in her Roland Garros title defence, Ostapenko has marched through the draw without dropping a set. Dominika played well and I was down in the first set and fought till the end.
"For me it's much sweeter to get to the semi-final here than in probably other grand slams because I didn't expect it", she said. She will need to hit the ground running in the semi-final to get to grips with the easy power.
Williams won Wimbledon on her last two visits in 2015 and 2016 before missing last year's event due to her pregnancy.
The two-time Grand Slam champion will take on the 21-year-old Latvian for the first time on Thursday. "I think for me it was important to be playing aggressive, trying to take the challenge of how she was playing".
Kerber, who offered up only a miserly seven free points, really just had to stay calm and wait for her opponent to self-destruct and Ostapenko fell into the trap.
"Obviously she has won so many titles here, not only here, a lot of grand slams beside Wimbledon", said Goerges, the 13th seed.
Perhaps she needs to stop thinking about Serena's status. Just going to prepare well for the match. "I really enjoy being here". Dreams can quickly turn to nightmares on a tennis court, so the strategy meeting that Goerges had planned with her team for Wednesday was set to be crucial.
Jeļena Ostapenko advanced to the Wimbledon semifinals, where she will play against Angelique Kerber, by beating Dominika Cibulková.
She hasn't dropped a set yet, has spent less than five hours in total on court through her first four matches, is averaging a 24 winner-count in each round, yet somehow Jelena Ostapenko has been flying under the radar at Wimbledon this fortnight.
Kerber, who won both the Australian Open and US Open in 2016, triumphed 6-3 7-5 on Centre Court to reach the semis.
"I think the match starts from zero".
With world No. 1 Rafael Nadal waiting for the victor, Tuesday's fourth set, played in much cooler conditions than the first three the day before, turned into a mini-epic before Del Potro eventually prevailed 7-6 (1), 7-6 (5), 5-7, 7-6 (5).
Kasatkina's serve remains a work in progress, however, and she gifted Kerber an early break with her first double fault of the match.
Simon failed to convert a break point, then a third match point for Del Potro ended with him netting a forehand.