[Editor's note: This story was updated at 4:05 p.m. CST Dec. 10.]

EQT Corp. (NYSE: EQT) is facing calls for a shakeup at the helm from shareholders Toby Rice and Derek Rice, who had sold Rice Energy to the Appalachia shale gas producer last year for $6.7 billion.

In a letter made public on Dec. 10, the Rice brothers, who own about seven million shares or a 2.75% stake in the company, pointed to EQT's "severely depressed" stock price and blamed the management for underperformance.

EQT shares have slumped 47.6% as of close on Dec. 7 since the acquisition of Rice Energy in November 2017, much worse than the 7.7% decline in the broader S&P 500 Energy index in the same period.

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The two brothers said that after several EQT investors reached out to them for help, they held talks with Chairman Jim Rohr and CEO Rob McNally, but there was a lack of 'reciprocal engagement.'

While calling for inclusion of individuals with experience in large-scale operational planning to the board and the senior management, the two brothers also sought greater authority for Toby Rice in the company's operations.

They said they were willing to work with the board, but had already identified replacements if an agreement could not be reached and are ready with a plan that would help generate an additional $400 million to $600 million pre-tax free cash flow per year.

EQT bought Rice Energy last year in a bid to expand its natural gas business, at a time when U.S. energy firms were spending heavily to develop facilities in gas-rich states like Pennsylvania, West Virginia and Ohio.

Meanwhile, EQT said it is "taking the right steps to deliver superior value." The company's shares were up 1.4% in early trading.