overall stamina and endurance depends on your lactic thresh-hold, your vo2 max (max aerobic capacity) and also on your overall levle of fitness which comprises of muscle stregnth, muscle efficency, muscles glycogen storage, the stregnth of your respitory muscles and also your cardiovascular system.
wether you need to run short distances fast or long distances at a more moderate pace, you still have to train running fast and moderatly.
as this is socer, you need to be bale to run long distances because the match goes on for a long time.
vo2 max is your maximum aeroibic capacity, the maximum is the point at which your are not using anairobic respiration. It is more to do with a stong hear that pumps a lot of blood then it is to do with the lungs.
to raise VO2 max you must do very intense excersize, like sprinting, and running up hill. This is called interval training, you run very fast for 3 minutes then jog slowly for 3 minutes then run fast for 3 minutes, do this for 30-60 min 2-3 days a week
your lactic threshold, well im not going to go in to what that is right now because i have heard some conflicting information and still have to make my mind up about it, but basicly the lactic threshold is the point at which lactic acid builds in your muscles and they burn. to raise this you must run at your lactic thresh hold which is the speed that if you carried on at, you would shortly have your muscles hurt. If you got for some longer intervals in your interval training mentioned above eg at least 1 10 min interval each session then you should raise the threshold and there for be able to go faster and further before it hurts.
this will all suplement your long distance running, it is vital for it, but you can not run short distances and then expect to be fine for long ones aswell.
make sure you run long distance aswell, 20km or so once a week as this will increase your endurance and make your muscles more efficent and allow them to store more glycogen.
the rest of the aspects mentioned at the start will all be worked on if you do what i said above, thats 4 days a week of running.
you could try weight training for your leg muscles but it is not to neccisery, and do not bother cross training with only a few weeks left as it will not help
just remember eat well so that includes 5 fruits a day, and low fat, but with all that excersize you have to make sure you pack in a lot of healthy carbs and get plenty of sleep.
you should have thought about tis earlyer because 2 weeks of training is not going to see huge results, it all takes time, im only telling you this stuff so you cna use it in the future, use it now anyway but do not expect to see large improvments in 2 weeks, although you will see small improvments.
to see moderate improvments you need to do it for 6 weeks but to get large improvments your talking 3 months and it can be 6 months before you get most of the improvment you are going to get. After 6 months the rate of improvment is already very slow, you have to do a lot more work to get a little improvment.
but good luck anyway and try this, it will not help much on such short notice but it will help in the future.
