A battle of giants, literally. 6'10" vs. 6'9", in Houston on clay. A nice quarter-final match.
Don't pay attention to the rankings and the surface, this will be close and a battle of serves.
The last time they played Isner came out on top in straights indoors in Memphis. This is their first meeting on clay, and Karlovic may actually be playing a little better than Isner right now.
Still, it's in America and Isner might have a little more consistency in his game if that is possible.
I like Inser 7-6. 7-6.