Sabalenka recorded her tour-leading 31st victory this season on the Madrid clay, adding the WTA 1000 trophy to titles in Brisbane and Miami.
The fourth-seeded Djokovic suffered a second consecutive opening defeat, after losing his opener against Alejandro Tabilo in Monte Carlo two weeks ago.
Iga Swiatek admits the strict doping protocols can be stressful for players but feels like she has "been through the worst" after surviving her positive test over contaminated melatonin.
The 38-year-old Spaniard, winner of 22 Grand Slam trophies, including 14 at Roland Garros, retired from the sport after his final match at the Davis Cup in Malaga in November.
The top-seeded Zverev, appearing in his first final since losing to Jannik Sinner in the Australian Open title decider in January, had little trouble dealing with Shelton, ranked 15 in the world.
The fifth-ranked Djokovic struggled to find his rhythm in a 6-3, 6-4 loss to Chilean Alejandro Tabilo in the second round, making an inauspicious start to his clay season.
The 19-year-old said that he had filled out his withdrawal form ahead of his match with Spaniard Roberto Bautista Agut and went to the referee's room -- but the official was out for lunch.
The Spaniard world number three, speaking ahead of the Miami Open, said he had not been given any notice of the legal case from the Professional Tennis Players' Association (PTPA) or the strongly-worded statement issued on Tuesday.
A four-time Grand Slam champion, Alcaraz said he was too focused on what weapons British left-hander Jack Draper might bring and unable to calm the pre-match jitters that prevented him from rising to the occasion.
Alcaraz, also the reigning Queen's champion, was beaten 7-6 (7/3), 6-3 by home favourite Jack Draper in the biggest win of the British number one's career.
Spanish tennis chiefs announced Wednesday that 22-time Grand Slam winner Nadal and newly crowned French Open champion Carlos Alcaraz would be part of the country's team at the Games next month.
"In Roland Garros, knowing all the Spanish players who have won this tournament and be able to put my name on that amazing list is something unbelievable," Alcaraz told reporters.
The world number one is just one match away from becoming the first woman to win the tournament in three straight years since Justine Henin in 2007 after a 6-2, 6-4 victory.
he injury, sustained in his fourth-round win over Francisco Cerundolo, ended the Serb's quest to win a record-extending 25th Grand Slam trophy and will result in him losing his top ranking to Italian Jannik Sinner on Monday.
Italy's Jasmine Paolini reached her first Grand Slam semi-final at the French Open on Wednesday after dumping out fourth seed Elena Rybakina 6-2, 4-6, 6-4.
"Due to a torn medial meniscus in his right knee (discovered during an MRI scan performed today), Novak Djokovic... has been forced to withdraw from the Roland Garros tournament," organisers said in a statement.
De Minaur had never got past the second round at the tournament before this year, winning just three of 10 matches.
The 24-time Grand Slam title winner made the last 16 by defeating Italy's Lorenzo Musetti in a bruising five-set epic which concluded at 3:07 am Sunday.
His four-hour 29-minute victory also allowed the 37-year-old world number one to equal Roger Federer's record of 369 Grand Slam match wins.
