Louis Oosthuizen is in the top spot on the leaderboard, but Jordan Spieth, who is one stroke off the lead after Thursday's first round, is the new favorite to win the 2021 Open Championship. Spieth is listed at 4-1 with Oosthuizen just behind him at 9/2, according to the updated odds at William Hill Sportsbook.

They are followed by Tommy Fleetwood and Collin Morikawa at 16-1 and then the trio of Dustin Johnson, Webb Simpson and Brooks Koepka is behind them at 20-1. Four strokes ahead of Koepka on the leaderboard is Brian Harman, who now sits at 22-1 despite being tied for second with Spieth. 

While the leaderboard and the odds board have a couple of Open winners at the top, there are handfuls of potential winners still in the mix with 18 golfers within three stokes of the lead heading into Friday's second round. Unfortunately, two of the week's biggest stars are not among that group in Jon Rahm and Rory McIlroy. Rahm was the betting favorite coming into this week's action at Royal St. George's, but he's now at 33-1 after shooting a 1-over round of 71 on Thursday and sitting outside the top 70 on the leaderboard. McIlroy was another top pick to win that saw his odds to win adjusted, now listed at 28-1 after shooting even par in a round that needed to be saved by a couple of late birdies. 

Check out the odds to win the 2021 Open Championship after the first round of action, per William Hill Sportsbook. 

2021 Open odds to win 

  • Jordan Spieth: 4-1 
  • Louis Oosthuizen: 9/2
  • Tommy Fleetwood: 16-1
  • Collin Morikawa: 16-1 
  • Dustin Johnson: 20-1 
  • Webb Simpson: 20-1
  • Brooks Koepka: 20-1 
  • Viktor Hovland: 22-1
  • Brian Harman: 22-1 
  • Scottie Scheffler: 25-1
  • Stewart Cink: 28-1 
  • Justin Rose: 28-1 
  • Rory McIlroy: 28-1
  • Xander Schauffele: 28-1 
  • Paul Casey: 33-1
  • Jon Rahm: 33-1
  • Sergio Garcia: 50-1