Its star soprano and tenor dropped out. Now the Metropolitan Opera’s hotly anticipated new production of Puccini’s “Tosca,” planned for next season, is losing its star conductor — and replacing him with a familiar baton.

The Met announced on Monday that Andris Nelsons, who leads the Boston Symphony Orchestra and, starting next season, the Leipzig Gewandhaus Orchestra in Germany, would not be conducting the “Tosca,” scheduled to open on New Year’s Eve. Mr. Nelsons “has withdrawn,” the company said in a statement, providing no further explanation.

But the Met has come up with an experienced replacement: James Levine, its music director emeritus, who led “Tosca” in his first performance with the company, on June 5, 1971, when he was 28. (“He brought to ‘Tosca’ a dramatic tautness frequently missing in the Met’s pit,” the critic Speight Jenkins wrote then, adding, “Levine should have a great career ahead of him.”)

Now 74, Mr. Levine stepped down as the Met’s music director last year because of health problems but remains a dominant presence on its podium. In addition to “Tosca,” next season he will lead Mozart’s “Die Zauberflöte” and a trio of Verdi works: “Il Trovatore,” “Luisa Miller,” and the Requiem.