Rafael Nadal starts his pre-retirement farewell tour against Carlos Alcaraz on Thursday at the Six Kings Slam, and Novak Djokovic faces Jannik Sinner at an exhibition event that awards money but no ATP ranking points and is Saudi Arabia’s latest foray into tennis.

Riyadh will host the WTA Finals next month to open a three-year deal as the kingdom continues to invest in various sports, despite concerns about LGBTQ+ and women’s rights there raised by Hall of Famers Chris Evert and Martina Navratilova and others.

In Wednesday’s matches at the Six Kings Slam, the top-ranked Sinner — who was cleared in a doping case shortly before winning the U.S. Open last month, although the World Anti-Doping Agency has appealed that exoneration - beat Daniil Medvedev 6-0, 6-3, and Alcaraz defeated Holger Rune 6-4, 6-2.

Nadal, an ambassador for the Saudi Tennis Federation, and Djokovic were given byes into the semifinals.

The matchup against Alcaraz will be the first contest for Nadal since his exit at the Paris Olympics in July — and his first match since he announced last week that he would be retiring after playing for Spain in the Davis Cup next month. Nadal and Alcaraz played doubles together at the Paris Games and could team up again for Davis Cup.

Looking ahead to Thursday’s exhibition, Alcaraz called Nadal a “legend” and “a really important person for my life, for my career.”

Djokovic and Sinner met for real on Sunday: Sinner won in straight sets to earn the trophy at the Shanghai Masters.

After a day off on Friday, the winners of Thursday’s two matches in Riyadh will meet in the event’s final on Saturday.

Nadal, 38, owns 22 Grand Slam titles; Djokovic, 37, has won 24, a record for the Open era.