They have played 4 times and Johnson leads 3-1. Their last meeting was in March 2015 in Indian Wells. Johnson won on a hard court in straight sets.
All their matches were on hard courts though one was indoors. There has been at least 1 tie break in every match. Johnson leads their tiebreaks 4-2.
It wasn’t rocket science to figure out that Johnson’s match with Isner would go to tie breaks. Both had only faced 1 break point in their previous matches this week and hadn’t been broken. In their quarter final Johnson faced and saved 6 break points. Isner again didn’t face one but still lost in 2 tie breaks.
Karlovic also came through his quarter final in 2 tie breaks. He saved all 4 of his break points and Sock saved the single break chance he gave on his serve.
This match has a look of the Isner v Johnson one. The market favourite has the better tie break record and leads the head to heads. Value is on Karlovic.
Backing servers is an option but I would wait for the server to be at 0-15 before entering. If a player gets broken there will be a large price move against you but we won’t see many breaks here.