Djokovic was pushed all the way by Cilic, and the overall numbers showed that he won just two more points than his opponent, the 2016 champion in Cincinnati, but it was his ability on the points that mattered that saw him through to a sixth final in the tournament.
Halep returned to the court and took control, running off four straight games for a 4-3 lead when rain arrived.
"I have learned that I don't have to give up, because anything can happen", she said.
Novak Djokovic of Serbia gestures after breaking Milos Roanic of Canada in the third set during the Western & Southern Open at Lindner Family Tennis Center on August 17, 2018 in Mason, Ohio.
His record in OH is mixed, having won all five previous semi-finals, he has gone on to lose all five finals that he has reached, three of those against Federer whom he could line up against on Sunday evening.
Top-ranked Simona Halep needed only eight points to complete a gritty comeback that was put on hold overnight by rain, beating qualifier Ajla Tomljanovic 4-6, 6-3, 6-3 at the Western & Southern Open on Thursday. He's won a record seven despite missing the tournament the last two years because of injury. Djokovic is trying to become the first player to win all nine events since the series started in 1990. "I have plenty of motivation".
Given such a discrepancy, it's unsurprising that Djokovic has been able to defeat Cilic on numerous occasions, and Cilic is 0-8 on hard court too, holding serve 64.1% with Djokovic being able to do so 89.4% of the time. "I'm in a good position, so I'll take it step by step". He got a different racket and started playing better.
He'll face Marin Cilic, who also won twice Friday to reach the semifinals.
"Waiting around all day and hardly seeing any tennis obviously is never fun for the tournament and the fans", Federer said. Then it was off for a little rest before playing Wawrinka, the second match of the day for both players.
Federer said he felt exhausted when he sat during the lightning delay, unsure whether the match would resume. Rain returned shortly after Halep left the court, delaying play again and creating chaos with the schedule. Fourth-seeded Juan Martin del Potro beat Hyeon Chung 6-2, 6-3, finally completing the second round in late afternoon. "I sat down and felt so heavy".
Halep has faced the most challenges from the rain, with one match suspended overnight Wednesday and then her third-round match held over for a day as well.
"But I've found out that I need to have the game B in the end of the day".
The Croatian won his only Masters title in Cincinnati and having missed the event a year ago his run this week meant he was riding a nine-game winning streak.
Ukrainian Svitolina, seeded fifth, beat 16-year-old American prodigy Amanda Anisimova 6-4, 6-4.