Canadian tenor Richard Margison will sing the role of Florestan beginning Feb. 12. (COC)

American tenor Jon Villars has walked off the set of the Canadian Opera Company's Toronto production of Fidelio and has had to be replaced at the last moment.

Icelandic tenor Jon Ketilsson and Canadian tenor Richard Margison have agreed to step in and fill the role of Florestan, the prisoner who narrowly escapes death.

Ketilsson, who has appeared as Florestan in Goteborg and Marseille, will sing the role for the first five performances of the Beethoven opera, beginning Saturday.

He arrives Thursday to rehearse with the COC cast, which includes the acclaimed Canadian soprano Adrianne Pieczonka as Leonore.

Margison, a Canadian tenor who last appeared with the COC as Calaf in Turandot in 2004, is performing for the first time with the COC at the Four Seasons Performing Arts Centre.

He performs the role Feb. 12-24.

It is not unusual for opera companies to have to fill a role at the last minute, usually because of illness.

Villars walked away from the role during a dress rehearsal performance before an audience at the Four Seasons centre Wednesday night, apparently because he was unable to master it, a COC spokesman said. He walked off stage near the end of the opera as his fellow cast members carried on without him.

He did not appear to be ill but "was not prepared for the role," she said.

Villars, who appeared five years ago in a COC production of Turandot, has previously sung the role of Florestan in Japan and Naples.