Here is a circuit of stretches using the Physio Ball that I am trying out with my athletes. We would complete this pre-workout, just after foam rolling, and/or post workout as part of our regeneration work. I really like using the ball for the stretches because it makes it easy to get the right amount of intensity and also helps position the athlete correctly. Often, players will "fake" stretch, and get into positions that kind of look right, but aren't.
By supporting themselves with the ball, we can easily keep natural spinal allignment, and use body weight to get the desired intensity, instead of trying to force a position which is uncomfortable. Most of these stretches were held for about 5 seconds in the video, or for 5 reps, but generally we would hold positions for about :20-:30 or move in and out of the stretch about 10 times.
The order goes like this:
1/2 Kneeling Quad/Hip Flexor
Hip Internal Rotation (mobility, not flexibility, but who's keeping track)