In State, ex rel. Martin, v. Columbus (1979), 58 Ohio St. 2d 261, paragraph two of the syllabus, this court held that a civil service employee who is unlawfully discharged is entitled to his lost compensation, but “is subject to have his claim reduced by the amount he earned, or in the exercise of due diligence, could have earned in appropriate employment during the period of exclusion.” In the third paragraph of the syllabus in Martin, supra, we held that this question of mitigation of damages “is an affirmative defense and the burden of proof on that issue resides upon the employer responsible for the wrongful discharge.” Thus, the issue before us is whether appellant city of Columbus has met its burden of proof.
*355Assuming, arguendo, that appellee did not exercise due diligence in seeking appropriate other employment, the burden is on appellant to establish what appellee could have earned in appropriate other employment. The record shows that Marshall was unlawfully discharged from the Columbus Department of Public Safety, Division of Fire, on the same day he graduated from the Columbus Fire Training Academy; that he placed third on Westerville’s firefighter civil service examination, but was not hired; that of the numerous individuals who took firefighter civil service examinations in Whitehall, Washington-Perry Township, and Grandview Heights, only 22 or 23 were ultimately hired; and that at the time Marshall could have competed for these latter positions he was suing appellant for reinstatement. Given these facts, we must agree that appellant has not met its burden of proof in establishing what appellee could have earned in appropriate employment if he had exercised due diligence.
Accordingly, the judgment of the Court of Appeals is affirmed.
Judgment affirmed.
Celebrezze, C. J., Herbert, W. Brown, P. Brown, Sweeney and Locher, JJ., concur.