One of retailer GameStop's biggest private investors has called on the company to make significant changes, and close stores, to help turn things around. The plan also includes a recommendation to scale down or close GameStop's businesses in Europe and Australia.

Through his venture capital firm RC Ventures, Chewy Inc. co-founder Ryan Cohen holds a 9.8 percent stake in GameStop's shares, making him one of the biggest investors. Cohen said in a letter that his attempts to discuss changes with management privately "yielded little progress," he's now reaching out to the board of directors to try to stir things up.

In the letter obtained by The Wall Street Journal, Cohen said GameStop "lacks the mindset, resources, and plan needed to become a dominant sector player." Cohen called out GameStop for its "apparent unwillingness to pivot with urgency and grow with gamers."