The German, who also pulled out of this week's Montreal Masters, was set to make his eighth appearance at the annual outdoor hardcourt tennis event in Ohio but it seems he's still not ready to return to competitive tennis.
Zverev tore several ligaments in his ankle during his French Open semifinal versus Rafael Nadal and has been stuck on the sidelines ever since.
The 25-year-old has since returned to the practice court, but while he was happy to report he felt no pain in his ankle in a recent interview with German media, he also noted that he was being "very careful" by not applying a lot of pressure on it.
"Of course, I moved very carefully, I haven't built up any pressure on my foot yet, but it's just good news that I really haven't had any pain at all - now we can move on," Zverev told n-tv.de.
The World No. 2 also said it was too early to comment on his US Open participation.
"It's too early [to make a decision about the US Open], I played tennis for the first time now," he said.
The 2020 US Open is the only Grand Slam tournament where Zverev has reached a final. He looked on course for victory after taking the first two sets against Dominic Thiem but let his advantage slip and had to look on as Thiem walked away with the prize.
Zverev also made headlines last week when he revealed he was a type 1 diabetic and was launching the Alexander Zverev Foundation to support children in developing countries with the same condition by proving insulin.