When you think about what makes up the foundation of a house, what is the first thing that comes to your mind? For me it is cement.
Yes, cement, a material that is strong and supportive, and allows building of a structure on a solid base of support. How solid that structure is will depend largely on the how well the cement was laid in that structure's foundation.
Athletic improvement is not all that much different as skill acquisition (improvement) and how much improvement can take place, is significantly based on how solid the foundation of the athlete's skillset is. And the first word that comes to my mind when discussing an athlete's foundation is fundamentals.
For more on this very important aspect of skill improvement, don't miss my piece titled Skill Acquisition at Weplay Moms: Expert Advice for Sports Parents.