I have to say that I found this videos by accident, but I'm glad I did it. These 3 videos are a very detailed tutorial that shows how photographer Matt Hernandez made his composite of the athlete George Wilson, from how he shot it, to how he extracted the subject from the original shot, how he shot the background, and then how it merged everything together to make a final image.

On the top of this post you can find the first part, but down here there are the part 2, which is how to prepare the background, and the part 3 which is how to blend the background with the foreground. Very interesting video tutorial, a bit long, but definitely worth it to watch it.