"It's been a month. Every time I talk it gets worse and worse," Rivera told the Post.
It has yet to be determined if Rivera will be forced to miss any time this spring. Despite the uncertain timeline, the right-hander has, in recent years, followed his own pace and regimen during Spring Training. Nevertheless, Rivera said he was treating the potential surgery with caution.
"When you are talking about surgery, nothing is simple," Rivera added.
The 41-year-old closer is coming off yet another strong season in which he set a new Major League record for career saves, finishing the year with 603. He eclipsed Trevor Hoffman's previous mark of 601 saves in a Sept. 19 game against the Twins.
Rivera went 1-2 with a 1.91 ERA and 44 saves, 60 strikeouts and eight walks in 2011. It was the fourth consecutive season in which Rivera finished with a sub-2.00 ERA and WHIP under 1.00.
Jon Star is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.