Hewitt pulled out of the Rogers Cup in Toronto after a persistent calf injury forced him to retire during the second set of his match against Columbian Alejandro Falla.
The current world number 30 told fans on his website that he had to focus on treatment and recovery with the US Open just under a month away.
"It's just one of those things that can happen and my focus now is to have treatment daily to enable me to play the Masters 1000 event in Cincinnati and then the US Open," he said.
"It is not the best preparation for a Grand Slam event, but there is nothing else I can do."
World number five Samantha Stosur has pulled out of next week's Masters 1000 event in Cincinnati with an arm injury that has caused her problems for close to a week.
Stosur sought medical advice after her quarter-final loss to Italy's Flavia Pennetta at the San Diego Open on Friday and was told to rest the injury.
There has been no word as to whether she will be fit for the US Open on August 30th in New York.
Sometimes it can be easy to lose sight of the big picture and get hung up on the set-backs we often experience on the way to achieving the goals we have set for ourselves.
A Well-Being Australia theologian reminds us that our timing can often be different from that of the Lord's.
Solomon in Ecclesiastes teaches about God's perfect timing.
"There is a time for everything, and a season for every activity under heaven...He has made everything beautiful in its time." - Ecclesiastes 3:1 & 11