Karlovic leads their previous meetings 2-1. Their last match was in March 2011 in Indian Wells. He won in straight sets on a hard court. They are 1-1 on clay. Karlovic has won their opening set in a tie break in all their matches.
Karlovic has won 2 of his last 10 on clay. In Istanbul last month he reached the semi finals losing in 2 tie breaks to Dimitrov. He lost in the first round of the French Open last year but reached the third round in 2014.
Montanes has had some decent runs on clay this year. His last tournament was the Hellbronn Challenger on clay earlier this month. He reached the semi finals.
I doubt this will be won in straight sets. Any sets that Karlovic takes is likely to be via a tie break. With their history we have a fair chance of Karlovic taking the opening set. I would give a slight edge to Montanes although if Karlovic has one of his superb serving days then Montanes will struggle to break him.
Laying the set 1 winner is an option. We could also back Karlovic at the start with part stake and green up when he takes the set. They start around 2.00 .