Cincinnati with a right wrist problem and subsequent scans revealed a tear in one of the tendons. Soon after that, he announced that he would miss the rest of the season. As a result of his extended absence, following the conclusion of Paris he fell to World No.22, his lowest ranking since January 2012 and his first time out of the top 20 in the rankings since March 2014. 2018: Return from injury & back to top 10 Nishikori returned after a 5-month injury layoff and started his 2018 season by playing at the American challenger tour events. In Newport Beach he lost in the first round against American qualifier Dennis Novikov. In the following week, Novikov and Nishikori met again in the first round. This time, Nishikori won in straight sets. Kei Nishikori went on to win his next four matches en route to win his sixth ATP Challenger career titles in Dallas, by defeating Mackenzie McDonald in the final. Nishikori made his return to the ATP Tour competition (since August 2017 Montreal) at the inaugural ATP 250 Tournament in New York. Nishikori made a back-to-back winning return in New York by defeating Noah Rubin and Evgeny Donskoy in the first and second round respectively. He defeated Radu Albot in the quarterfinals in three sets, before losing to Kevin Anderson in the semifinal. Kei Nishikori was unseeded at the 2018 Abierto Mexicano Telcel in Acapulco and lost against Denis Shapovalov in the first round. In a bid to regain match fitness, Nishikori entered the Monte-Carlo Masters for the first time since 2012, having never progressed past the third round at the tournament before. Unseeded for the tournament, he beat Tomas Berdych, Daniil Medvedev, Andreas Seppi, Marin Cilic, and Alexander Zverev to reach his 4th career Masters 1000 finals, before losing to Rafael Nadal in straight sets in the finals. He thus became the active player with the most Masters 1000 finals without a title. At the 2018 Italian Open, he advanced past Feliciano López, third seed Grigor Dimitrov, and Philipp Kohlschreiber before losing to Novak Djokovic in the quarterfinals in three sets. At the 2018 French Open, Nishikori was seeded 19th. He defeated Maxime Janvier, Benoît Paire, and Gilles Simon before falling to seventh seed Dominic Thiem in the fourth round. In the lead up to Wimbledon, Nishikori lost to Karen Khachanov in the 2nd round at the Halle