#4 Marin Cilic
Marin Cilic is a supremely talented player who many believe hasn't done full justice to his potential. The Croat is one of the very few Slam champions in the French Open draw, having won the US Open in 2014, and he also has multiple runner-up finishes to his name - at the 2017 Wimbledon and 2018 Australian Open, where he lost to Roger Federer both times.
The 30-year-old has stated that doing well in the upcoming French Open will give him the much-required boost to regain his form and touch. He has struggled to put together more than a couple of match wins this year, and is in desperate need of a good result.
Cilic's strong baseline play has always unsettled his opponents. He has a powerful serve that can repeatedly help him get out of trouble, and he moves very well for a 6'6" player.
Cilic has also worked on his volleys, and can finish points effectively at the net. Although the Croat hasn't won any tournament this year, he is capable of outplaying the best of opponents on his day.