Tunisia s Ons Jabeur is out for revenge against Elena Rybakina (AFP)
Daniil Medvedev has a difficult task against unseeded Christopher Eubanks in his quarter-final and women's second seed Aryna Sabalenka faces American Madison Keys.
World number one Alcaraz is fast getting used to grass as he prepares to take on his friend Holger Rune on Centre Court.
The two players are both only 20 but Alcaraz already has a Grand Slam under his belt -- the US Open last year
"I'm really excited about this match," he said. "We shared a lot of great moments. We played together since we were 12 years old.
"We've not texted each other, but obviously we know each other really well. Yeah, I'm really excited about it. I think he's the same."
Alcaraz may be top seed at the All England Club but Novak Djokovic is the strong favourite -- and is not afraid to say so.
The Serb star reached his 12th Wimbledon semi-final and record-equalling 46th at the Grand Slams with a four-set victory over Russia's Andrey Rublev on Tuesday.
"I don't want to sound arrogant, but of course I would consider myself favourite," said Djokovic, who will play Italy's Jannik Sinner in the last four.
"Judging by the results I had in my career here, the last four times at Wimbledon that I won, so I do consider myself favourite, yes."
In the other men's quarter-final on Wednesday, former US Open champion Medvedev faces a tricky tie against Eubanks, who is ranked 43rd, on Court No. 1.
The American has fallen head over heels in love with grass after previously describing it as the "stupidest" surface to play on.
- Revenge mission -
Sixth seed Jabeur has made no secret of the fact she is out for revenge when she takes on Rybakina
The Tunisian, who has fast become a crowd favourite at the All England Club, was a set up last year against the Kazakh player before the final slipped away from her.
Jabeur said losing the match was "painful" but that she gave everything.
"I believe in destiny," she said. "It wasn't supposed to be that year. Maybe greater things are coming after that final. Definitely will learn a lot from it."
Keys has kept a relatively low profile at this year's tournament but suddenly finds herself back in the quarter-finals, eight years after she last reached the same stage.
The American, seeded 25th, dropped her first set of the tournament in her impressive three-set win over Russian 16-year-old Mirra Andreeva.
Belarusian second seed Aryna Sabalenka has won three tournaments this year, including the Australian Open, and has looked increasingly impressive.
Ukrainian wild card Elina Svitolina and unseeded Czech player Marketa Vondrousova progressed to the semi-finals on Tuesday.
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