When Serena Williams' serve wasn't getting her all the points she needed at Wimbledon, she turned to her return game.
Job done, and then some.
Williams reached the semifinals at the All England Club for the 12th time, overcoming five breaks of serve to beat Alison Riske 6-4, 4-6, 6-3 Tuesday on Centre Court.
"It's a long, arduous road," Williams said. "It's not easy."
The seven-time Wimbledon champion, who owns 23 major titles overall, was broken twice early in the first set despite six aces, trailing 3-1 and 4-3, but she broke back each time and then again to take the set.
Williams landed 81% of her returns (25 of 31) in that first set and won more than 50% of the points on both Riske's first serves and her second serves. That return percentage dropped slightly to 76 in the second, but it jumped back up to 81 in the third.
She won the match with an ace, her 19th of the day. Williams had served only 22 aces in the previous four rounds.
"She was really so close to taking the win today," Williams said. "She was playing her heart out. She had nothing to lose and I realized I didn't either. I need to just do better."
Riske, who upset top-ranked Ash Barty in the fourth round, had never before faced Williams on the tennis tour and was playing in the quarterfinals of a Grand Slam tournament for the first time. She certainly took advantage of every chance she had, converting each of the five break points she created.
Williams will next face either 19th-seeded Johanna Konta or Barbora Strycova on Thursday in the semifinals. But first, she'll be back out on Centre Court later Tuesday to play mixed doubles with Andy Murray.
On No. 1 Court, former No. 1 Simona Halep beat Zhang Shuai 7-6 (4), 6-1 to reach the Wimbledon semifinals for the second time.
Halep, who beat teenage sensation Coco Gauff in straight sets in the fourth round, is the highest seeded woman left in the draw at No. 7.
Zhang led 4-1 in the first set and had four break points, but Halep saved them all.
Later Tuesday, Konta, the last British player in the tournament, was to play Strycova on Centre Court, while No. 8 Elina Svitolina was facing Karolina Muchova on No. 1 Court.