Good fighters are bad runners. For mice and men, a strength in one area of Darwinian fitness may mean a deficiency in another. A look at Olympic athletes shows that a wrestler is built much differently than a marathoner. It's long been supposed that strength in fighting, or protecting territory and resources, comes at the expense of running, or spatial mobility. Now an experiment with house mice provides evidence for this theory. Source 6d.
Strength and speed are both important to one degree or another. But in truth, having lived a life where I can assess what's most important in my line of work, I think reflexes trumps both. Granted, my line of work isn't a sport. Let me explain, you need some amount of strength in the military. You can be a carrying a rucksack and gear weighing anywhere from 40lbs to a 140lbs, and a bit more on occasion. This takes strength. You need speed because there will be times you are either chasing or being chased. But it is reflexes that keep you alive when the bullets start flying, the IEDs start going off, and the unexpected happens.
Depending on the sport you will need strength or speed. Sometimes both. Track is where you need speed and endurance. Football both strength and speed can be beneficial. It all depends on the sport but I can see many sports where speed is important and others where speed is important. Endurance in the sport is always a must.