Sources with Nadal's team said before he took the court Tuesday for a practice session that, despite the pain he felt during his 7-6 (8-6), 3-6, 7-6 (7-4), 6-4 win Monday over Argentina's Juan Martin del Potro, the test revealed no major cause for concern.
"After the match I went to take an MRI at a London hospital. During the match I thought I had something serious - but as the match went on the pain got better and thankfully the tests don't show an injury," Nadal said Tuesday on Facebook.
The pain flared up in the 12th game of the match and prompted Nadal to take an eight-minute injury timeout before the first-set tiebreaker so a trainer could examine the back part of his foot.
The world No. 1 told reporters after the match that he thought he may have broken his foot and was close to retiring from the tournament, but he decided to play on after the trainer wrapped the foot heavily.
With the win, the 2008 and 2010 champion advanced to the Wimbledon quarterfinals for the fifth time and will square off against a rejuvenated Fish, who has achieved a career-high ranking of No. 9 and become the top-ranked American at the age of 29.
Wimbledon is the third of four Grand Slam events on the tennis calendar and the only one played on grass.