Based on my experience, all other factors being equal, a martial arts student starting out as an experienced athlete will progress more quickly than a student who starts out without that background. Contributing factors include:
If the athlete doesn't have the same motivation and dedication to their martial art as they did to their previous sport, then they won't get as far. If a great basketball player tries Karate, but finds it boring, then they won't become a great karateka.
The skills and attributes required by the prior sport can vary in how much they carry over to a given martial art. From my experience teaching BJJ, I'd say that rock climbing, gymnastics, American football, soccer, rugby, powerlifting, and strong man competition all give a significant advantage for new BJJ students. I imagine that a baseball player would have some advantage over a complete couch potato, but the benefits would probably not be nearly so great.
I say all this as someone who came into martial arts with minimal athletic experience or talent. It took me years to reach the point that some of my students reach in a few months.
- Kinesthetic awareness
- Balance
- Experience learning physical skills
- Physical conditioning allowing more training time and intensity
- Mental fortitude to push through physical discomfort and frustration
- ... and many more
If the athlete doesn't have the same motivation and dedication to their martial art as they did to their previous sport, then they won't get as far. If a great basketball player tries Karate, but finds it boring, then they won't become a great karateka.
The skills and attributes required by the prior sport can vary in how much they carry over to a given martial art. From my experience teaching BJJ, I'd say that rock climbing, gymnastics, American football, soccer, rugby, powerlifting, and strong man competition all give a significant advantage for new BJJ students. I imagine that a baseball player would have some advantage over a complete couch potato, but the benefits would probably not be nearly so great.
I say all this as someone who came into martial arts with minimal athletic experience or talent. It took me years to reach the point that some of my students reach in a few months.