Hewitt beat Wimbledon quarter-finalist Mikhail Youzhny 6-4 6-4 at the Cincinnati Open on Monday, making a good switch to the hard court surface after some decent form on grass.
The 31-year-old pushed Novak Djokovic to three sets before losing at the London Olympics and in July he reached the final at Newport, Rhode Island, where he lost to American John Isner.
Blake, who has twice reached the quarter-finals at the US Open, is ranked 106th in the world but reached the last eight at the Washington Open earlier this month.
Two-time NCAA champion Steve Johnson of the US and Frenchman Guillaume Rufin also earned wild card berths into the main draw for the August 27-September 9 US Open, which is the final Gram Slam tournament of the year.
- Novak Djokovic
- Mikhail Youzhny