Exhibit 99.4

ATHLON ENERGY INC.

UNAUDITED PRO FORMA FINANCIAL STATEMENTS

INTRODUCTION

Athlon Energy Inc. (“Athlon”), a Delaware corporation, incorporated on April 1, 2013 and is an independent exploration and production company focused on the acquisition, development, and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin.  On April 7, 2014, Athlon entered into purchase and sale agreements with Hibernia Holdings, LLC (“Hibernia”) and Piedra Energy II, LLC (“Piedra”) to acquire certain oil and natural gas properties and related assets in the Permian Basin in West Texas for $667.7 million in cash, in the aggregate (the “Acquisitions”).  The accompanying unaudited pro forma financial statements give effect to the Acquisitions, including related financing transactions.  The unaudited pro forma balance sheet assumes that the Acquisitions and related transactions occurred on December 31, 2013.  The unaudited pro forma statement of operations assumes that the Acquisitions and related transactions occurred on January 1, 2013.

The accompanying unaudited pro forma financial statements should be read together with: (1) Athlon’s audited consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2013; (2) Hibernia Energy LLC’s audited consolidated financial statements as of and for the year ended December 31, 2013, which is included as an exhibit to this Current Report on Form 8-K/A; and (3) Piedra’s audited Schedule of Direct Operating Revenues and Direct Operating Expenses of Certain Oil and Natural Gas Properties, which is incorporated by reference into this Current Report on Form 8-K/A.

The accompanying unaudited pro forma financial statements were derived by making certain adjustments to Athlon’s historical consolidated financial statements.  The adjustments are based on currently available information and certain estimates and assumptions.  Therefore, the actual adjustments may differ from the pro forma adjustments.  However, management believes that the assumptions provide a reasonable basis for presenting the significant effects of the transactions as contemplated and that the pro forma adjustments give appropriate effect to those assumptions and are properly applied in the unaudited pro forma financial statements.

The unaudited pro forma financial statements and related notes are presented for illustrative purposes only.  If the Acquisitions and related transactions had occurred in the past, Athlon’s operating results might have been materially different from those presented in the unaudited pro forma financial statements.  The unaudited pro forma financial statements should not be relied upon as an indication of operating results that Athlon would have achieved if the Acquisitions and related transactions had taken place on the specified date.  In addition, future results may vary significantly from the results reflected in the unaudited pro forma statement of operations and should not be relied on as an indication of the future results Athlon will have after the completion of the Acquisitions and related transactions.

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ATHLON ENERGY INC.

UNAUDITED PRO FORMA BALANCE SHEET

December 31, 2013

(in thousands)

The accompanying notes are an integral part of these unaudited pro forma financial statements.

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ATHLON ENERGY INC.

UNAUDITED PRO FORMA STATEMENT OF OPERATIONS

For the Year Ended December 31, 2013

(in thousands, except per share amounts)

The accompanying notes are an integral part of these unaudited pro forma financial statements.

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ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS

Note 1.   Basis of Presentation, the Offering, and Other Transactions

Athlon’s historical financial information is derived from Athlon’s consolidated financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2013, which is incorporated by reference into this Current Report on Form 8-K/A.  Hibernia Energy LLC’s historical financial information is derived from Hibernia’s audited consolidated financial statements as of and for the year ended December 31, 2013, which is included as an exhibit to this Current Report on Form 8-K/A.  Piedra’s historical financial information is derived from Piedra’s audited Schedule of Direct Operating Revenues and Direct Operating Expenses of Certain Oil and Natural Gas Properties, which is incorporated by reference into this Current Report on Form 8-K/A.  Piedra’s Schedule of Direct Operating Revenues and Direct Operating Expenses of Certain Oil and Natural Gas Properties is not intended to be a complete presentation of the results of operations of the properties, as they do not include general and administrative expenses, effects of derivative transactions, interest income or expense, depreciation, depletion, and amortization, any provision for income tax expenses, and other income and expense items not directly associated with direct operating revenues from natural gas, natural gas liquids, and crude oil.  As such, they are not indicative of the operating results of the Piedra assets going forward.

For purposes of the unaudited pro forma balance sheet, it is assumed that the Acquisitions and related transactions occurred on December 31, 2013.  For purposes of the unaudited pro forma statement of operations, it is assumed that the Acquisitions and related transactions occurred on January 1, 2013.

Note 2.   Pro Forma Adjustments and Assumptions

Athlon made the following adjustments and assumptions in the preparation of the unaudited pro forma balance sheet:

(a)         On April 11, 2014, Athlon received firm commitments from the lenders under its credit agreement to increase the borrowing base from $525 million to $1.0 billion.  Reflects estimated debt issuance costs associated with this borrowing base redetermination.

(b)         Reflects borrowings under Athlon’s credit agreement to fund the purchase price of the Acquisitions.

(c)          To eliminate the assets, liabilities, and members’ equity not acquired or assumed from Hibernia in the Acquisitions, to record the Acquisitions for $667.7 million in cash, and to allocate the purchase price to the assets acquired and liabilities assumed.  The allocation of the purchase price to the assets acquired and liabilities assumed is preliminary and, therefore, subject to change.  Any future adjustments to the allocation of the purchase price are not expected to have a material effect on Athlon’s financial condition, results of operations, or cash flows.

The allocation of the purchase price of the Acquisitions to the fair value of the assets acquired and liabilities assumed is as follows (in thousands):

(d)         Reflects estimated acquisition costs incurred in connection with the consummation of the Acquisitions.

Athlon made the following adjustments and assumptions in the preparation of the unaudited pro forma statement of operations:

(a)         A portion of the assets acquired by Hibernia were acquired by them during May 2013.  Reflects the incremental oil and natural gas revenues and production costs associated with those assets Hibernia from January 1, 2013 through the date of acquisition.

(b)         Reflects incremental depletion, depreciation, and amortization of oil and natural gas properties associated with the Acquisitions.  Costs associated with evaluated properties are amortized using a unit-of-production basis under the full cost method of accounting for oil and natural gas properties.

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ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS — Continued

(c)          Reflects incremental accretion of discount on asset retirement obligations associated with the Acquisitions.

(d)         Reflects estimated incremental interest expense associated with borrowings under Athlon’s credit agreement to fund the purchase price of the Acquisitions and amortization of incremental debt issuance costs associated with the aforementioned borrowing base redetermination.

If the LIBOR rate increased 1/8%, we would have incurred approximately $1.0 million more of interest expense and if the rate decreased 1/8%, we would have incurred approximately $1.0 million less.

(e)          Reflects estimated incremental income tax provision associated with the additional operating income from the Acquisitions and the pro forma adjustments using Athlon’s effective tax rate for 2013 of 24.1%.  This rate is inclusive of federal, state, and local income taxes and differs from the statutory rate as Athlon has only been subject to federal income tax as a subchapter C corporation since the date of its incorporation.

(f)           Reflects estimated increase in net income attributable to noncontrolling interest associated with the additional operating income from the Acquisitions and the pro forma adjustments.  Athlon is the sole managing partner of Athlon Holdings LP and owns less than 100% of the economic interest in Athlon Holdings LP, but has 100% of the voting power and controls the management of Athlon Holdings LP.

Note 3. Pro Forma Earnings Per Share

The following table reflects the pro forma allocation of net income to Athlon’s common stockholders and earnings per share (“EPS”) computations for 2013 (in thousands, except per share amounts):

Note 4.         Supplementary Information

There are numerous uncertainties inherent in estimating quantities of proved reserves and in projecting future rates of production and timing of development expenditures.  Oil and natural gas reserve engineering is and must be recognized as a subjective process of estimating underground accumulations of oil and natural gas that cannot be measured in any exact way, and estimates of other engineers might differ materially from those included herein.  The accuracy of any reserve estimate is a function of the quality of available data and engineering, and estimates may justify revisions based on the results of drilling, testing, and production activities.  Accordingly, reserve estimates are often materially different from the quantities of oil and natural gas that are ultimately recovered.  Reserve estimates are integral to management’s analysis of impairment of oil and natural gas properties and the calculation of depletion, depreciation, and amortization on these properties.  Natural gas volumes include natural gas liquids.

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS — Continued

Athlon’s estimated pro forma net quantities of proved reserves were as follows as of December 31, 2013:

The changes in Athlon’s pro forma proved reserves were as follows for 2013:

The following pro forma standardized measure of the discounted net future cash flows and changes applicable to proved reserves reflect the effect of income taxes assuming the Acquisitions had been subject to federal income tax.  The future net cash flows are discounted at 10% per year and assume continuation of existing economic conditions.

The standardized measure of discounted future net cash flows, in management’s opinion, should be examined with caution.  The basis for this table is the reserve studies prepared by independent petroleum engineering consultants, which contain imprecise estimates of quantities and rates of production of reserves.  Revisions of previous year estimates can have a significant impact on these results.  Also, exploration costs in one year may lead to significant discoveries in later years and may significantly change previous estimates of proved reserves and their valuation.  Therefore, the standardized measure of discounted future net cash flows is not necessarily indicative of the fair value of Athlon’s proved oil and natural gas properties.

The data presented should not be viewed as representing the expected cash flow from or current value of, existing proved reserves since the computations are based on a large number of estimates and arbitrary assumptions.  Reserve quantities cannot be measured with precision and their estimation requires many judgmental determinations and frequent revisions.  Actual future prices and costs are likely to be substantially different from the prices and costs utilized in the computation of reported amounts.

Athlon’s pro forma standardized measure of discounted future net cash flows was as follows as of December 31, 2013:

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ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS — Continued

The changes in Athlon’s pro forma standardized measure of discounted estimated future net cash flows were as follows for 2013:

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