Dominant on clay, Swiatek barely put a foot wrong, making just eight unforced errors in the match to leave the American with virtually no chance.

The top seed started in unforgiving form, breaking to love in the second game and dropping just three of the first 17 points.

Keys, seeded 18th, battled back to hold from 0-30 down for a 3-1 deficit, fighting to stay in the set.

However, last year's Madrid runner-up broke again for a 5-1 lead and served it out to wrap up the first set in 31 minutes.

Swiatek broke for a 2-1 lead in the second set with a superb passing shot and never relinquished her advantage, even though Keys was more competitive.

The four-time Grand Slam winner broke once more to seal her victory when world number 20 Keys went long.

"I feel really good," Swiatek said. "I wasn't really thinking about what happened last year. But repeating this result is a great thing.

"I'll have a chance to play a nice match in two days. So it's really exciting. I'm happy overall with the whole tournament."

Later reigning champion and second seed Aryna Sabalenka faces Elena Rybakina in the second semi-final. In the men's quarter-finals, Daniil Medvedev plays Jiri Lehecka, aiming to join Andrey Rublev, Taylor Fritz and Felix Auger-Aliassime in the final four.