P-Dub,
It doesn\'t have to be one horse, it can be a multi-horse box. But if you look back in this thread, I think you can make a case for \"one horse\" as well. Without seeing all the sheets yet, the two fastest horses besides Big Brown are Hey Byrn and Gayego. Hey Byrn had a negative one in early February (roughly). He has had 12-15 weeks since the big figure and is rested coming into this. He will be 25-1 or so and is faster than anybody besides Big Brown, has tactical speed to get a good trip, and could be set for a return to his top.
The other one, IMO, could be Gayego. Sheet purists might not like him coming back in two weeks, but he ran so little in the Derby, one could argue it was more like a tough workout, than a real race. (not a great argument, which is why he is 2nd on my longshot list, not 1st). He ran his \"0\" five weeks ago. Another will good tactical speed, possibly enough speed to get a 1w/1w trip on the lead. Figures 15-1 or so.
But Big Byrn is very live here, at a very large price, IMHO.