He again returned to the ATP World Tour in February 2016 after a long injury-induced absence. At the 2016 Summer Olympics he discovered a huge vein of form, defeating World No. 1 Novak Djokovic in straight sets in the first round and No. 3 Rafael Nadal in the semi-finals, claiming silver after falling in the final to No. 2 Andy Murray in four attritional sets. Only weeks later, Murray and del Potro met again in the Davis Cup semi-final in Glasgow, with del Potro emerging victorious in 5 sets. He then led Argentina to their first ever Davis Cup victory by defeating Croatia's Marin Čilić in the final in Zagreb. He reached his first major semi-final since 2013 by defeating Roger Federer in the quarter-finals of the 2017 US Open. In 2018, he won his first Masters 1000 title at the Indian Wells Masters, defeating defending champion and World No. 1 Roger Federer in the final. After reaching the semi-finals of the 2018 French Open, he again matched his career high of No. 4. Finally, in August, he achieved the World No. 3 ranking for the very first time. At the 2018 US Open, he reached his second Grand Slam final.