Padres manager Bud Black opted to use pitcher Sean O'Sullivan as a long reliever Friday against the Cardinals.

O'Sullivan pitched the seventh and eighth innings Friday, allowing three runs and five hits. It was his first relief appearance since April 6, 2011 with the Royals. Black will continue to use the right-hander as a long reliever, in case a starter were to get into some early trouble.

"[Friday], I didn't feel very prepared for the situation," O'Sullivan said. "But I won't let that happen again."

O'Sullivan has a 6.43 ERA in seven innings this season.