Southeastern Asset Management, which holds a 13.9 percent stake in Oklahoma City-based Chesapeake, said the share price implies a gas price below that of benchmark futures contracts traded on the New York Mercantile Exchange. Memphis, Tennessee- based Southeastern commented in a U.S. Securities & Exchange Commission filing Monday.

The stock price also doesn’t reflect any value for Chesapeake’s portfolio of unproven reserves, Southeastern said.

Southeastern CEO O. Mason Hawkins urged Chesapeake’s board to “be open to any offers to acquire the whole company” in a May 7 letter to directors. He also said any offer would have to recognize “the longer-term value of the company.”

Chesapeake fell 4.1 percent to $17.61 at the close in New York. The shares have declined 21 percent this year amid growing investor mistrust of Chief Executive Officer Aubrey McClendon’s use of personal stakes in company-operated wells to obtain private loans.

McClendon is being forced to step down from the chairman’s role and half the non-executive directors will be replaced later this month by nominees of Southeastern and billionaire investor Carl Icahn.