Babson College, along with London Business School, launched the Global Entrepreneurship Monitor (GEM) in 1999 to help answer this very question.

FORBES: High Impact Entrepreneurship: Following the Entrepreneurial Process

It might not always pan out, but a willingness to give someone a chance to come off the bench during a critical project might help you discover a real gem.

FORBES: Lin-Sanity and Nurturing Talent