World number one Novak Djokovic withdrew on Monday from this month's Western & Southern Open in Cincinnati, saying he needed more time to recuperate from a season in which he won three Grand Slam tournaments and competed at the Tokyo Olympics.
"I'm taking a bit longer to recover after quite a physically taxing journey from Australian Open up to Tokyo," he wrote on Twitter.
"Sadly, this means I won't be ready to compete in Cincinnati this year so I'll be turning my focus to the U.S. Open and spending more time with my family.
"Can't wait to see you in New York soon!"
Djokovic, a 20-time Grand Slam champion, is a two-time champion at the Masters 1000 hardcourt event played at the Lindner Family Tennis Center in Ohio.
Djokovic had won all three of the Grand Slam tournaments he entered this year and had sought to be the first man to win all four and an Olympic gold in a calendar year.
But those plans were dashed when he lost to eventual gold medallist Alexander Zverev of Germany in the Olympic semi-final and then to Spain's Pablo Carreno Busta in the bronze medal match.
The Western & Southern Open runs from Aug. 14 to Aug. 22.