Korir is the most accomplished guy in the race aside from Rupp and a very old Bernard Lagat. Korir has much faster 10k at 27:20, sub 60 half marathon, and 2:07 marathon when he wasn't even training for the marathon. He ran that race a few weeks after the world championships 10k race.
With Rupp's injury question marks I'd say Korir is more of a lock than anyone in the field including Rupp.
And people saying Ward would run 2:08 on a flat course, maybe, but I'll believe it when I see it. He ran upper 2:09 on a net downhill Boston course. The same one Ryan Hall ran his non-legal 2:04 PR. Boston is a fast course if you don't have crap weather and pace it correctly (hobby joggers hit the wall no matter what, so when they get the hills after 20 miles they slow down more than elites).
So to answer the question, besides Rupp who has the best shot at being top 3? It is easily Leonard Korir.