Johnson, who is seeded 19th in this year's tournament, was down 6-4, 6-1, 5-2 to Russian Evgeny Donskoy, but saved six match points to take the set and eventually the match (4-6, 1-6, 7-6, 6-3, 6-3).
Johnson showed a similar strength of spirit in his quarterfinal matchup against Great Britain's Andy Murray in the Olympics. Johnson didn't win a game in the first set, but came back to take the second, 6-4. He ultimately fell in the third-set tiebreaker to the eventual Olympic champion, but earned well-deserved praise for the tenacity he displayed.
Next up for Johnson is Argentinean Juan Martin del Potro, who won the US Open in 2009.
Comeback complete. @SJohnson_89 saves multiple match points, rallies from two sets down+past #Donskoy in 5. #usopen https://t.co/RpsZcOKjdM
-- US Open Tennis (@usopen) August 31, 2016
