Rory McIlroy: WGC Matchplay all-USA draw for world number one

Rory McIlroy will play three round-robin matches in the WGC Match Play Championship

Rory McIlroy has been drawn against three USA players in the World Golf Championships Matchplay, which starts in San Francisco on Wednesday.

The world number one, 25, faces Billy Horschel, Brandt Snedeker and Jason Dufner in the new round-robin format.

The world's top 16 are the leading seeds in 16 groups of four players at TPC Harding Park. Group winners progress to the knockout stage.

Justin Rose, Ian Poulter and Masters champion Jordan Spieth also feature.

Spieth is in the same group as England's Lee Westwood, while Rose, winner of the Zurich Classic of New Orleans on Sunday, opens his campaign against Australian Marc Leishman on Wednesday.

Northern Irishman McIlroy will start against 53rd seed Dufner, who won the 2013 PGA Championship, before tackling 35th seed Snedeker on Thursday.

He rounds off his Group 1 campaign on Friday against last year's FedEx Cup champion and 18th seed Horschel.

The group winner will face the player who tops Group 16, which features Japan's Hideki Matsuyama, American Kevin Na, Dutchman Joost Luiten and Alexander Levy of France.

The round of 16 and quarter-finals are played on Saturday, before the semi-finals and final on Sunday.

Australia's Jason Day returns to defend the tournament he won in 2014.

Draw (seeding/name/nation):

Group 1: 1-Rory McIlroy (NI), 18-Billy Horschel (USA), 35-Brandt Snedeker (USA), 53-Jason Dufner (USA)

Group 2: 2-Jordan Spieth (USA), 26-Lee Westwood (Eng), 40-Matt Every (USA), 62-Mikko Ilonen (Fin)

Group 3: 3-Henrik Stenson (Swe), 23-Bill Haas (USA), 42-Brendon Todd (USA), 60-John Senden (Aus)

Group 4: 4-Bubba Watson (USA), 29-Louis Oosthuizen (RSA), 33-Keegan Bradley (USA), 63-Miguel Angel Jimenez (Spa)

Group 5: 5-Jim Furyk (USA), 17-Martin Kaymer (Ger), 44-Thongchai Jaidee (Tha), 59-George Coetzee (RSA)

Group 6: 6-Justin Rose (Eng), 22-Ryan Palmer (USA), 34-Anirban Lahiri (Ind), 56-Marc Leishman (Aus)

Group 10: 10-Sergio Garcia (Spa), 30-Jamie Donaldson (Wal), 39-Bernd Wiesberger (Aut), 54-Tommy Fleetwood (Eng)

Group 11: 11-Jimmy Walker (USA), 27-Ian Poulter (Eng), 46-Webb Simpson (USA), 50-Gary Woodland (USA)

Group 13: 13-Rickie Fowler (USA), 32-Graeme McDowell (NI), 47-Shane Lowry (Ire), 55-Harris English (USA)

Group 14: 14-Matt Kuchar (USA), 31-Hunter Mahan (USA), 41-Stephen Gallacher (Sco), 61-Ben Martin (USA)

Group 15: 15-Patrick Reed (USA), 29-Ryan Moore (USA), 49-Danny Willett (Eng), 61-Andy Sullivan (Eng)

Group 16: 16-Hideki Matsuyama (Jap), 21-Kevin Na (USA), 44-Joost Luiten (Ned), 54-Alexander Levy (Fra)