Soriano's opt-out had been expected since the end of the season. His agent, Scott Boras, has indicated to several media outlets, including ESPNNewYork.com, that he planned to advise his client to opt out and become a free agent.
Soriano would have been paid $14 million had he remained for the final season of the deal. Soriano can negotiate with all teams beginning Saturday.
If Rivera decides to return, there is very little chance the Yankees will try to re-sign Soriano, who saved 42 games in 45 opportunities filling in for Rivera since early May.
Rivera is still contemplating whether to play next season. Immediately after suffering his season-ending knee injury, he vowed to pitch again, but backed off that stance last week when he informed Yankees general manager Brian Cashman that he is undecided on his future.
With Soriano opting out, the Yankees have leeway to offer Rivera more money. If Rivera retires and the Yankees don't re-sign Soriano, then David Robertson, Joba Chamberlain and David Aardsma would be in-house candidates for the closer role.
The Yankees' team offices have been closed due to Hurricane Sandy. Yankee Stadium suffered only minor damage from the storm.