Krajinović, and reached the final without dropping a set after Fabio Fognini retired before the start of their semifinal match. He faced unseeded Nikoloz Basilashvili in the final, losing 4–6, 4–6. He then competed in the Shanghai Masters seeded third. He defeated Richard Gasquet and faced 13th seed Borna Ćorić in the third round, narrowly dropping the first set before he retired due to a knee injury. This injury later forced his withdrawal from the rest of the season and the ATP Finals, for which he had qualified for the first time since 2013. 2019–2021: Continued injuries Del Potro's injury lingered into the 2019 season, forcing him to withdraw from the Australian Open. He made his comeback at Delray Beach Open where he reached the quarterfinals, losing to Mackenzie McDonald in three sets. Still not having recovered from injury, Del Potro chose not to defend his titles in Acapulco and Indian Wells, withdrawing from both tournaments. Playing in his first tournament back at the Madrid Open, del Potro lost his first match to Laslo Đere. He then played in Rome and secured wins against David Goffin, who had a 3–1 lead over him before the match, and Casper Ruud. He squandered two match points in a second set tiebreaker to ultimately lose his quarterfinal against world number 1 Novak Djokovic over a three-hour match. In the French Open, del Potro was seeded 8th but lost in the fourth round to Karen Khachanov. In his first grass tournament of the season at Queen's Club, del Potro suffered another career-threatening injury when he fractured his kneecap in his first round match against Denis Shapovalov. Del Potro did not play any professional tennis from 2019 at Queen's Club until 2022 at the Argentina Open. He underwent four right knee surgeries (June 2019, January 2020, August 2020 and March 2021) and withdrew from the Tokyo Olympics in July. At the 2021 US Open, del Potro reported that his knee was getting better, he had picked up training on the court again and hoped to be ready to play on the tour within a couple of months. 2022: Return to professional tennis, potential retirement On 31 January, it was announced that Del Potro will make his return to professional tennis at the 2022 Argentina Open, where he accepted a wild card. He also accepted a wild card to play the 2022 Rio Open. On 5