Our deepest fear is not that we are inadequate. Our deepest fear is that we are powerful beyond measure.
There is nothing enlightened about shrinking so that other people won't feel insecure around you.

He's suggesting his players are not being all they are capable of as they are holding back. Perhaps not doing as good as they might so as not to show one another up. Least that how it appears to me. Not seen it but that's my assumption.

I answered this on Saturday --

The entire quote is: "Our deepest fear is not that we are inadequate. Our deepest fear is that we are powerful beyond measure. It is our light, not our darkness, that most frightens us. Your playing small does not serve the world. There is nothing enlightened about shrinking so that other people won't feel insecure around you. We are all meant to shine as children do. It's not just in some of us; it is in everyone. And as we let our own lights shine, we unconsciously give other people permission to do the same. As we are liberated from our own fear, our presence automatically liberates others."

In other words, be your best self, and don't "shrink" so others feel big. By being your best self, you encourage others to also be their best selves.