The in-form Aussie laboured throughout the round of 32 match as his heavy schedule over the past month seemingly caught up with him.
Kyrgios also required a physio to attend his knee towards the end of the match with the US Open now less than a fortnight away.
Former US Open finalist Greg Rusedski was worried about what he saw from Kyrgios against Fritz with the crowd left disappointed by the Aussie’s lack of fight.
“He’s improved out of sight but physically he’s got to get stronger.
“You’re worried about the knee physically. It’s a lot easier to do on grass courts than hard courts.”
Kyrgios, who won his first ATP singles event in three years at the Citi Open earlier this month, has played 12 singles matches in August to date.
His defeat to Fritz was only his second loss from those 12 encounters having also fallen to Hubert Hurkacz in the quarter-finals of the Canadian Open.
On top of his singles commitments, the 27-year-old has been playing men’s doubles and won the Atlanta Open alongside Thanasi Kokkinakis before completing a historic Citi Open double with Jack Sock.
While all those matches have helped Kyrgios rediscover career-best form and a top 30 ATP ranking, his latest outing suggests a break is dearly needed ahead of the US Open.
The Australian had been backed as a genuine contender for the tournament having also made the Wimbledon final in July.
Andy Roddick hailed Kyrgios’ incredible run in Washington earlier this month and believes such a showing means he has to be viewed a US Open favourite.
“To go through singles and doubles and not to tap out mentally or physically is a big, big sign,” Roddick said on the Tennis Channel.
“I think it puts him into the top two, maybe three, favorites for the U.S. Open.”
It was a disappointing day overall for Aussies in Cincinnati with Alex de Minaur also beaten convincingly 6-3 6-2 by Felix Auger-Aliassime.
