I’m not a sports man so I don’t know any of these players, but it does seem like they all have very individualistic attributes that you captured well.
It seems to me your forms are conveyed pretty well, and the caricatures are effective, exaggerating the right parts that don’t detract from the likeness. There are some issues here and there with how the forms read–specifically, the rate of turn on some forms aren’t accurate enough, with some curved forms appearing pinched (the fifth one’s cheeks, for example).
Your brushwork is a bit smudgy in some areas, and I think you might want to practice a more alla prima approach where you’re letting the brushstrokes lay on expressively with careful control, instead of going back and trying to blend/smudge too much, which tends to kill spontaneity and expressiveness. You should analyze master painters and see how they approach brushwork–especially watch videos of them painting live session. For example, Richard Schmid’s captain’s portrait DVD is extremely good at demonstrating how a master paints in a very short amount of time, an amazing portrait in real-time: http://www.richardschmid.com/product-p/stcp-0002.htm
His books are amazing too–particularly Alla Prima II and The Landscapes.
Other painters you might want to study: John Singer Sargent, Anders Zorn, Joaquin Sorolla, Pino Daeni, Suzanne Lyon, Zhaoming Wu, Huihan Liu, Daniel Gerhartz, Morgan Weistling, Nathan Fowkes, Jeremy Lipking, etc.
For more commercial works, take a look at master illustrators like Haddon Sundblom, Gil Elvgren, J.C. Leyendecker, Norman Rockwell, Andrew Loomis, Harry Anderson, etc.