With The Open officially on the horizon, a pair of names remain at the top of the betting board for Royal Portrush.

Major magician Brooks Koepka opened as a 6/1 favorite at the Westgate Las Vegas SuperBook when odds were released after the U.S. Open at Pebble Beach, with Rory McIlroy next in line at 10/1. But the market has drawn them together in recent weeks, with Koepka and McIlroy both now listed as 8/1 co-favorites with the season's final major just a week away. Dustin Johnson, who opened at 12/1, remains at the same odds behind only the co-favorites.

McIlroy famously set the Portrush course record with a 61 at age 16, while Koepka has finished first or second in each of the first three majors this year.

Jon Rahm's win at the Irish Open drew some attention from bettors, as Rahm's odds fell from 20/1 to 16/1 over the weekend. That puts him alongside Tiger Woods, who opened at 12/1 after Pebble Beach and has since drifted slightly from the top spot.

Here's a look at the betting odds on some of the pre-tournament favorites, with the spotlight shifting to Northern Ireland in a matter of days:

8/1: Brooks Koepka, Rory McIlroy

12/1: Dustin Johnson

16/1: Tiger Woods, Jon Rahm

20/1: Francesco Molinari, Justin Rose

25/1: Rickie Fowler, Xander Schauffele, Patrick Cantlay, Tommy Fleetwood

30/1: Justin Thomas, Jason Day, Jordan Spieth, Hideki Matsuyama, Bryson DeChambeau, Adam Scott, Louis Oosthuizen

40/1: Matt Kuchar

50/1: Henrik Stenson, Paul Casey, Graeme McDowell, Gary Woodland, Matt Wallace

60/1: Sergio Garcia, Tony Finau, Shane Lowry, Marc Leishman, Patrick Reed

80/1: Phil Mickelson, Ian Poulter, Webb Simpson, Matthew Fitzpatrick, Rafa Cabrera-Bello

100/1: Danny Willett, Eddie Pepperell, Tyrrell Hatton

125/1: Chez Reavie, Zach Johnson, Kevin Kisner, Brandt Snedeker, Lee Westwood, Martin Kaymer

150/1: Scott Piercy, Abraham Ancer, Bernd Wiesberger, Daniel Berger, Sungjae Im, Russell Knox, Keegan Bradley, Thorbjorn Olesen, Alex Noren, Haotong Li, Branden Grace, Bubba Watson