Creutz, who has a neutral rating on the stock, added that history is full of examples of CEOs who have built young companies but cannot manage them when they mature.
Asked about his voting shares, Pincus told Reuters he decided to retain such huge control over Zynga because he believed from the start that he was the best person to lead the company.
"Investors who want to see the company deliver long-term value are going to be better served by the fact that I can continue to ensure the company keeps its focus on the long term and we don't let short-term swings and opportunities reduce that," he said in an interview.
Based on Friday's closing share price, the value of Pincus' holdings fell to $1.05 billion from $1.1 billion at the IPO price.
Friday's flop stunned investors who had expected a strong showing because the company is profitable, unlike other recent high profile Internet IPOs such as Groupon and Pandora .
"I was stunned when I saw this. This is a disaster for them. The way you're supposed to price deals is to give investors a 15 percent IPO discount to compensate them for the risk of backing a relatively new company," said Dan Niles, chief investment officer of AlphaOne Capital Partners, who did not buy shares.
"It makes me wonder about the underlying health of the market. IPOs like this can change the whole tenor of the market," he added.
Investors said Zynga's stock performance could hurt other private companies in the pipeline such as Yelp and even Facebook. Some investors regard Zynga's IPO as a proxy for Facebook, because 95 percent of its $828 million in revenue in the past nine months comes from Mark Zuckerberg's social network.