ATP Umag (clay)
Martin is decent clay courter with plenty of experience. He won this tournament in 2016 and this is one of his favorite places to play. Conditions here are slower than on most of other clay courts on tour and that's what suits his game.
Caruso has only won 6 matches on clay this year of which only one was on main tour. On Challenger tour he struggles to win unless he's playing on his home soil. Martin on the other hand has 21 wins on clay this season of which just 5 were on main tour, but 4 of them came in other tournament on Balkans Peninsula, in Belgrade to be specific, where he lost in semi-final to great Novak Djokovic in three sets.
Maybe Martin is not in his prime, but he never really drops below certain level while Caruso has one of the worst seasons of his professional career. I expect Slovakian to win in straight sets here.