Improving power, or explosive strength and speed is a big deal in soccer. Ask a player what he feels he needs to work on and 9 out of 10 the answer will be: "get faster and more explosive"
And they are right, these qualities are definitely very important for a dominating performance in soccer and many other sports. Note: I am not a scientist, and I do not know much about research, so I would like to simply give you my personal take on this based on experience and logic.
This advice comes straight from the trenches. Theory is good, but it has to be backed by practice, in my opinion. I do a lot of work with association football (soccer) and my approach has proven effective over and over again: for myself as many others, applying the same strategies.