Strength, power or sport-specific work: which gap do you actually need to fill?

Strength is the foundation, and you have to train it. But for athletes who are already strong, adding more maximal strength won't necessarily make them faster: international-level rugby players trained for a year and added 9 kg to their power clean, yet their sprint got no faster at all.
The reason is simple: in competition, the time available to produce force is mostly under 0.3 s. Work out first whether you're missing strength, power or sport-specific ability, then decide what to train.
The references are on the last two slides.