The head-to-head may not always be an accurate way to prognosticate but at least it's objective since it's based on past performances.
Both Andy Murray and Stan Wawrinka are in the top upper half of the 2017 Wimbledon men's draw, but based on the head-to-head, Italy's Fabio Fognini is the player to most likely reach the semi-final spot on their side of the draw, even if his most successful run here is just to the 3rd round.
Fognini has been to the quarters of the French Open and the 4th round in the US and the Australian Open so he can be a dangerous player.
Wawrinka is already out of the race, losing to Russian Daniil Medvedev in the first round. Interestingly, Fognini has a winning record over Andy Murray, Lucas Pouille and Jo-Wilfried Tsonga, all potential players that he may meet in the next rounds, that's why he's the tip for this side of the draw.
If he does hold up his win-loss record over these guys, it would be a historic moment for him. Otherwise, any of those three guys are just as capable of getting the semifinal slot, on this side of the draw.