 He capped a successful summer with his second top-5 finish at a WGC event when he finished 4th at the WGC-Bridgestone Invitational.That finish moved him into the top-25 of the OWGR.In September 2017, the European Tour announced that it would be returning to Belgium for the first time in 18 years with Pieters hosting the Belgian Knockout – a unique strokeplay and matchplay format – in May 2018.