Whitlock produced an amazing comeback fron 9-3 down to defeat Jamie Caven 10-9, winning the deciding leg with a sublime 146 checkout when his opponent was waiting on 56.
“That came from the heart,” said defending champion Whitlock, who will face Ronny Huybrechts this evening.
“I was thinking about when Andy Hamilton did it to me at the World Matchplay a couple of years ago and I just hung in there and weathered the storm.
“Jamie lost his way a bit when I started coming back and I do feel for him but I am the defending champion and I don’t want to let this title go.”
van Gerwen averaged 105 as he defeated Jelle Klaasen with a brilliant performance, which included seven 180s and a 136 finish for the world number two.
“I really wanted to win this game and I’m very happy to have won it,” said van Gerwen, who takes on Adrian Lewis in the last four.
“It was a quality game and I’m very pleased to be through to the semi-finals.
“I’m looking forward to tonight because I know I can play even better than this so hopefully I can keep on improving in this tournament.
“I think I am the favourite but that means nothing and I’ll make sure I’m prepared for a tough opponent.”
Robert Thornton was denied a semi-final spot after losing out in a last leg decider to Huybrechts.
Lewis defeated Andy Hamilton in the afternoon’s other match.
By Chris Murphy
Bronze tickets are still available to see van Gerwen, Whitlock, Wade, van Barneveld, Priestley, Huybrechts and Winstanley at OVER THE TOP in Barnsley on September 27 – GET YOURS HERE