Jeff D'Amico, the scheduled starting pitcher, and second baseman Rob Mackowiak were last-minutes scratches because of flu-like symptoms that also affected pitching coach Spin Williams.
Pat Mahomes stepped in for D'Amico to make his first start since Sept. 27 with the Cubs, holding the Marlins hitless until Juan Encarnacion singled leading off the fifth and Derek Lee homered into the Pirates' bullpen in center field.
McClendon was forced to switch to Mahomes only five minutes before the game started, barely enough time for Mahomes to warm up.
"He did an outstanding job under the circumstances," McClendon said. "He made his pitches and got ahead in the count for the most part."