Wells Fargo Securities analyst Mike Mayo is wondering who will replace Citigroup (C - Get Report) Chairman Michael O'Neill, who is set for mandatory retirement at the end of 2018.

"Who's going to be chairman of Citigroup?," Mayo pondered in an interview with TheStreet, adding that former Goldman Sachs (GS - Get Report) COO Gary Cohn could be a contender. Cohn recently departed his White House job as National Economic Council Director. 

Mayo also pointed to Harvey Shwartz, the Goldman Sachs co-president set to retire in April. 

"I think it's the right question for shareholders to ask," Mayo said. "The stock has performed poorly and I think it's up to us collectively to keep the pressure on Citigroup."

Mayo plans to ask Citigroup about the Chairman role at the bank's annual shareholders meeting on April 24 in Chicago.

Citigroup shares are down 4.8% year-to-date, compared to a 0.85% decline for the S&P 500.

Mayo said he's torn on CEO Michael Corbat taking on the chairman role. "Citigroup missed some of its prior targets - they are actually 5 years behind in their target for return on assets," Mayo noted, adding that he does give Corbat for reducing risk at Citigroup in recent years.

Citigroup and Goldman Sachs are holdings of Jim Cramer's charitable trust Action Alerts PLUS. 

Watch full conversation with Mike Mayo on our Youtube Channel