Djokovic was defeated by Roberto Bautista Agut and Marin Cilic in the semi-finals and quarterfinals in Shanghai and Paris. As a result of this, he lost the No. 1 ranking to Andy Murray. However, a runner-up finish at the World Tour Finals indicated his best performances in nearly three months. After the season, he parted ways with his coach of three years, Boris Becker. In January, Djokovic defended his title in Doha defeating new world No. 1 Andy Murray in three sets. At the 2017 Australian Open, he was upset in the second round by No. 117 Denis Istomin of Uzbekistan. This was the first time since 2007 that Djokovic had failed to reach the quarterfinals at the Australian Open, and the first time ever in his career that he had lost to a player ranked outside of the top 100 in a Grand Slam tournament. In February and March, Djokovic played at the Mexican Open and the Indian Well Masters, but in both events was eliminated by Nick Kyrgios, in the third and fourth rounds, respectively. In April, Djokovic reached the quarterfinals of the Monte-Carlo Masters, losing to David Goffin. After the tournament, he decided to split with his long-time coach Marián Vajda, fitness specialist Gebhard Phil-Gritsch and physioterapeut Miljan Amanović, citing the need to find a winning spark. A better showing at the Madrid Masters saw Djokovic reach the semi-finals, losing to Nadal in straight sets. A runner-up result at the Rome Masters indicated solid improvements in his form. On 21 May 2017, he announced that Andre Agassi would become his new coach, starting at the 2017 French Open. However, as the defending champion, he lost at Roland Garros in the quarterfinals to Dominic Thiem. He prepared for Wimbledon at the Eastbourne International, playing his first non-Wimbledon tournament on grass since the 2010 Aegon Championships. He won the tournament, beating Gaël Monfils in the final. This marked his first grass title outside of Wimbledon. He made it to the quarterfinals at Wimbledon before retiring against Tomas Berdych while down a set and a break, due to an elbow injury which he said had been bothering him for a year and a half. On 26 July, Djokovic announced that he would miss the 2017 US Open and the rest of the 2017 season to fully recover from his elbow injury.