Soccer is a passion of mine, I have played since I was 6 years old. I have been very fortunate to train several pro soccer player over the years and have developed a pretty straight forward way to get fit fast. The protocol is designed for a pretty fit high school player all the way up to the pros. All of these intervals are based on 1 minute of work, so a 45/15 interval would be 45 seconds of a brisk jog and 15 seconds of a sprint. I use 50 yds as a distance, this way you can open up your stride length.You will be running back and forth for the duration of your workout. These workouts will be done twice a week, and at the end of a training session. This will take 9 weeks and if you are honest and if you train hard, you will reap the benefits. This training regimen will replace long distance running.
Weeks 1-3#1 45/15 for 5 min
#2 45/15 for 6 min
#3 45/15 for 7 min
#4 45/15 for 8 min
#5 45/15 for 9 min
#6 45/15 for 10 min
Weeks 4-6#1 40/20 for 5 min
#2 40/20 for 6 min
#3 40/20 for 7 min
#4 40/20 for 8 min
#5 40/20 for 9 min
#6 40/20 for 10 min
Weeks 7-9#1 35/25 for 5 min
#2 35/25 for 6 min
#3 35/25 for 7 min
#4 35/25 for 8 min
#5 35/25 for 9 min
#6 35/25 for 9 min
A few thoughts....Conditioning is all in your head, keep your head down and train hard every step you take.
Be honest when you sprint, when it's time to sprint, you better be moving!
Make sure you turn in both directions at the end of each 50yd marker, you do not want to create imbalances by only turning one way.
Never act tired, act as if you have been there before and you are comfortable. Never let your opponent see you fatigued, be mentally tough. Make sure they quit before you do.
I have done this, it works. I would never prescribe a routine that I haven't done myself. Practice what you preach.