Simon has won all 6 of their previous matches. He won them all in straight sets.Their last meeting was in April 2016 on clay.
Simon was in real trouble in the last round. He was 2 sets down to Pella and the 3rd, 4th and 5th sets were very tight.
Troicki beat Dimitrov in the first round but has a shorter match in the last round when Lajovic retired in their third set.
I don’t see Simon taking this in straight sets. He will be tired and if he gets a 2-0 lead he will look to save energy for the next round. He could also be slow to start and may lose the opening set. I think Simon comes through in 4 sets.
Wait for Simon to be broken first or to lose the opening set before backing.