ive been working out for a few weeks now each body part once a week 8-12 reps x 12 sets total for combined legs/calves. I decided to take a week off thsi week since ive started to play a lot of basketball once more. Ive noticed more explosion in my jumps and rebounding but after just two days i think i may have found a weakness in my legs...my upper quads (not near knee) are very sore and so are my hip flexors. Any way to strengthen these more when i continue my exercise program so that my vertical continues to progress?

The old grandma, squats. Lunge is great also but don't just got forward with your front foot. Use a 12 to 6 o'clock pattern on each foot.

IE you lunge with your right foot - First you will got straight ahead (12 o'clock) next using the right foot you go out at 11 o'clock. Back, 10 o'clock etc to 6 o'clock: 6 reps on each leg.

ive been working out for a few weeks now each body part once a week 8-12 reps x 12 sets total for combined legs/calves. I decided to take a week off thsi week since ive started to play a lot of basketball once more. Ive noticed more explosion in my jumps and rebounding but after just two days i think i may have found a weakness in my legs...my upper quads (not near knee) are very sore and so are my hip flexors. Any way to strengthen these more when i continue my exercise program so that my vertical continues to progress?

The hip flexors raise the knee towards the chest, something a squat doesn't do. Try this for the hip flexor (http://www.exrx.net/WeightExercises/HipFlexors/LVHipFlexion.html) I've also used a leg extension machine for the hip flexor by putting the pad that normally goes on top of the ankle on top of my knee instead. You may also use a leg curl machine in a similar fashion.

not feeling good...my quad feels like someone punched it hard...had serious pain playing today

I've had that soreness from starting up in basketball or running after a break. Are you sure it's not just the initial soreness that will go away after a few days back at it? Or are you asking for exercises that will specifically strengthen that part of your body?