What influences development the most?
There are so many things and mentality is right up there at the top but I’m certain that playing lots of small sided games is absolutely key for any player to become great.
Almost all of the best players I played with in 11-a-side were also the best small sided players. There were a few exceptions and it was generally the physical beasts who were able to stand out in 11s without being great at the small sided game. However, I think the rule generally holds true; the best (or most impactful) players in the full size game are also the best in the small sided game.
Why are small sided games so beneficial?
Small sided games develop game intelligence and pattern recognition like nothing else. Those aspects are vital in football because you have to think quickly and recognize patterns in milliseconds, especially at the higher levels. Playing small sided games is just an incredible way to help players improve.
You get more touches. You get less time. You get more pressure. You get more involvement in the game. All of these things combined over a long period of time contribute to outstanding development.
Personal experience convinces me this is true
Playing lots of small sided games gave me a huge advantage over players who didn’t have that experience, I’m certain of that. I played so many indoor 5v5 games over a period of 10+ years and I am 100% certain that those games and the experiences in them were responsible for the majority of my development.
It wasn’t coaches (respectfully) and it wasn’t genetics (bluntly, I have average genes). My game IQ and ability to instantly recognize patterns and passing options was the result of playing small sided games (it helps that I played against adults when I was a kid so I was pushed to do things quicker all the time).
Players, parents, coaches, all take note
If you are a player, get involved in as many small sided games as you can. Futsal, indoor football, 5v5 competitions, anything where the numbers are lower and you get lots of game involvement.
If you are a parent, get your kid involved in the sessions described in the previous paragraph.
If you are a coach, make sure your players are getting lots of small sided game exposure in training and also playing small sided competitive games as much as possible.
Small sided games are crucial for player development. Don’t let anybody tell you otherwise.