Currently second in the WRX drivers' points, Gronholm won the season-opener in Abu Dhabi before being handed a post-race penalty and dropping to second. He then finished fourth in round two in Spain.

But after being admitted to hospital in recent days, the 22-year-old will now undergo an appendicitis operation in Finland and will miss WRX's first event at Belgian Grand Prix Formula 1 venue Spa.

Gronholm's GRX team had already entered a third Hyundai i20 at Spa for 2014 Global Rallycross champion Joni Wiman.

He will now be nominated to score teams' points as the Marcus Gronholm-owned squad reverts to running just two cars.

Duval gets ES Skoda call-up

Fresh from winning a round of the French Rallycross Championship last weekend, former works WRC driver and European rallycross race winner Duval will race for the ES Motorsport team at Spa, replacing reigning Super1600 champion Rokas Baciuska.

Duval has been a regular competitor in his home round of World RX in recent years in a range of machinery.

Baciuska's absence from Spa comes as a surprise, given he had been expected to contest the full season for ES.

"I am very happy be present for this first event on the Spa-Francorchamps track," said Duval.

"It all came together at the last minute. I know it will not be easy to be competitive against the other teams and cars because I do not know the team or the car, but I come without pressure and to enjoy."