Long story short, if you don't spar, you can't fight.
Actually you can. Every normal human being can fight naturally. Usually martial artist (mostly those pseudo traditional ones) suggest that without martial arts training the fighting ability would be at 0% and that there would be a clear line between a martial artist and a non-martial artist. Try to take away the newborn baby of a mother and she will prove them wrong. Sure, specific fighting training can (drastically) improve the fighting ability though and that's were I am with you again. Sparring is an absolute important factor to get as much access as possible from your maximal natural fighting potential
. So for (successful) competition you imperativly need sparring.