Just under two weeks before they were set to play their first regular-season game -- on opening night against the defending champion Golden State Warriors -- the Oklahoma City Thunder received some unfortunate injury news. 

Swingman Andre Roberson has suffered a setback in his return from a ruptured patellar tendon, and will need a knee surgery that is expected to keep him out at least two extra months. Via ESPN:

Oklahoma City Thunder guard Andre Roberson will miss at least an additional two months after undergoing a procedure Thursday following a setback during his rehab from left knee surgery, a Thunder spokesperson said.

After suffering a ruptured patellar tendon in January, Roberson was on track to return to the floor in November, but he needed an additional procedure because a suture was causing irritation that he couldn't play through.

This comes in addition to an arthroscopic surgery Roberson had on his knee over the summer to address some inflammation. The one bit of good news for the Thunder is that Roberson is reportedly healing well from the patellar tendon injury, and this additional surgery is just to remove a suture and not fix anything else in his knee. 

Still, this is a tough blow for the Thunder. Roberson is not only the Thunder's best defender, but one of the best players in the league on that end of the floor. Working in tandem with Paul George -- a strong defender in his own right -- the Thunder had a devastating duo on the wing to contain opponents' best offensive players. 

But if that wasn't enough, the Thunder are also pretty thin on the wing. Alex Abrines will likely slide into Roberson's starting position, but behind Abrines are only three relatively untested youngsters: Timothe Luwawu-Cabarrot, Terrence Ferguson and Abdel Nader. Not exactly a bunch of household names. 

In a loaded Western Conference, Roberson's setback could prove costly for the Thunder. With Russell Westbrook, George and Steven Adams they should be able to hold things together well enough that they won't be in danger of missing the playoffs. But it's not inconceivable that this injury ends up costing them home-court advantage in the first round of the playoffs.