I think the biggest problem is your light source. It's all over the place with no apparent rhyme or reason. It's a prime reason why your leg looks funny. One leg is lit from one direction and the other leg from a completely different direction. It creates a weird shadow in the groin area that's very obvious. The shadow on the chest makes no sense judging by the drop shadow on the cloak. Again, you have two distinctly different light sources. Even the horns are lit from two different directions.
The cloak is very flat and appears to be striped. However, I would assume you were going more for the folded look, in which case you didn't nail it at all. I would have created flowing folds along the bottom of the cloak to create a more interesting 3 dimensional appearance and shaded it accordingly.
As far as his pose goes it needs to be much more dynamic and should include some foreshortening to give it more depth. Perhaps even varying weights of line work would help. In my opinion any line work with the aid of some solid black shading would help because without it it's gonna be real hard to make this a one color cut vinyl or screen print type design. I think a sports icon should be clean, bold, and strikingly simple.
All in all, I really think you did a fair job, but there is a lot of room for improvement. Judging by appearance, I would guess that cartoon illustrations aren't your strong point.