Monster Energy AMA Supercross, an FIM World Championship, contender Josh Grant will miss the next six to eight weeks of the 2010 title chase after electing to undergo surgery on a shoulder injury suffered in the lead-up to Anaheim 1’s season opener last weekend.

With advice from his doctors, Grant has decided to repair a labrum tear in his right shoulder after attending the round one and trying his best to ride, but after qualifying for the main event he could not continue due to the pain and the inability to hold on well enough.

Grant will undergo surgery Friday, before rehabilitating his shoulder and returning to action.

It has also been confirmed that Queenslander Dan Reardon is out for the second round at Phoenix this weekend after suffering a grade two concussion in his scary heat race crash at Anaheim.

Speculation on American message boards have Aussie privateer Michael Byrne on the short list to ride for Grant’s Joe Gibbs Racing MX/Toyota Yamaha team should it require a replacement rider as Grant sits out.

Byrne was left without a ride for this season despite finishing fourth in the AMA Motocross Championship on a Rockstar Makita Suzuki in 2008 and 2009. Read our interview with the Queenslander from this week here.