NEW YORK ( TheStreet) -- To break a stock, the goal of a short like Greenlight Capital's David Einhorn isn't getting the retail investor to run scared, it's to get the big institutional holders of shares to capitulate. In the case of Green Mountain Coffee Roasters ( GMCR), this means the most important "tell" will be what mutual fund giant Fidelity Investments does -- or has already done -- in response to the demise of Green Mountain Coffee shares.Fidelity is the largest shareholder of Green Mountain Coffee Roasters as of its last quarterly portfolio report, through June 30. That report, filed with the Securities and Exchange Commission on Aug. 16, showed that the mutual fund giant had increased its stake in Green Mountain Coffee by 4.7 million shares during the second quarter, to 19.1 million shares. The second-quarter buying by Fidelity was a 32% increase in its Green Mountain stake, and represents 12.5% of Green Mountain's outstanding shares, according to the Imetrix service from Edgar Online. Overall, Green Mountain shares are 75%-owned by institutional investors.