"I'm excited to introduce Max Mirnyi as a new part of my coaching team, and I'm curious to see what the future holds," Nishikori wrote on Instagram. Mirnyi should support the 29-year-old as a full-time coach.

Belarussian Mirnyi ended his 22-year career at the end of 2018. He was at the top of the ATP double rankings for 57 weeks, winning 52 tournament victories, six of them at Grand Slam tournaments. In the individual he reached in 2003 with his 18th place more than remarkable Career High. This season he also won his only single tournament in Rotterdam.

Other achievements include a quarter-finals at the US Open (2002) and a gold medal at the 2012 Olympics with Viktoria Azarenka.

"I'm excited about being able to help Kei, and I've known him from my playing days because we spent a lot of time together at the IMG Academy in Bradenton," Mirnyi said. "I hope that this cooperation works well for both of us."

Nishikori is currently ranked 13th in the ATP world rankings, but has not played since the US Open. In October, he underwent surgery on his right elbow. At the other three Grand Slams in 2019 he reached the quarter-finals, in Brisbane he got at the beginning of the season the only season title. At the ATP Cup Nishikori plans his comeback on the tour.

Only in October, Nishikori separated from long-term coach Dante Bottini.