David Epstein's The Sports Gene talks about several areas where it's a feedback loop between nature and nurture:

• One's starting point, of how much an untrained or unpracticed person is able to do something, is a big influence on whether someone even starts down that formal track.
• Simple access to training resources is a big determinant of whether a person will try those things. That's why pro hockey players tend to be born in the early months of the year, or why so many bobsledders are from Upstate New York.
• People respond differently to training, and how quickly one improves influences a lot of whether that person intends to continue putting in the work.
• People's ceilings are in different places. For many sports, being world class literally requires certain genetic coding: very long limbs, very accurate eyesight, very high Achilles tendons, certain biological adaptations for altitude or holding one's breath, etc. Someone who is only slightly taller than average will struggle to make it into the NBA, no matter how much practice.
• The internal drive to practice possibly has a genetic component, too.

But outside of all of that, it also matters whether we're talking about becoming a world class athlete or just a hobbyist. For weekend warriors running a 5k in a pack of thousands of participants who paid to be there, practice and training are going to be far more important predictors of their performance than any kind of genetic or innate talent. The genetic or innate bottlenecks might show up in the Olympics, but not the amateur hobbyist runners.