Matchup is favorable to Dimitrov, he leads 2-0 and usually can make Querrey uncomfortable pretty easily with his mixed play. In those two matches, Dimitrov broke Querrey 7 times in 5 sets, which is a quite good percent against a bot+ player, specially considering the matches were played in fast hard of Washington and grass of Queens.
But I have a bad feeling about this one, Grigor spent to much time in the court those last 7-8 days and Querrey should be very tough to break in this surface. I think Samantha will bot his way through his service makes and will take advantage from a couple of those lapses the bulgarian is prone and will take the match in two close sets.
Hopefully I'm wrong though, would be great to see a Fog vs. Dimi match in QF's.