Rodriguez will be required to complete a pre-surgery strengthening program of four to six weeks, similar to the one Mariano Rivera had on his right knee this year, and he could have the procedure scheduled in January.
It is believed, Cashman said, that the injury was a contributing factor in the disappointing postseason that forced manager Joe Girardi to repeatedly bench and pinch-hit for Rodriguez.
"The struggles we saw in September and in October are more likely than not related to this issue," Cashman said. "Clearly, Alex was dealing with an issue. ... He wasn't firing on all cylinders."
According to Cashman, Rodriguez first reported discomfort to Girardi in Game 3 of the AL Division Series against Baltimore after he was lifted for pinch-hitter Raul Ibanez, but Rodriguez said his right hip was bothering him.
An MRI exam taken at a New York hospital showed no problems. It was not until November, when Rodriguez had a routine checkup at the Vail, Colo., offices of Dr. Marc Philippon -- who performed the February 2009 surgery on Rodriguez's right hip -- that the left hip injuries were identified.
Cashman said that he is confident Rodriguez will be on the field for the Yankees at some point in 2013.
"I have no reason to believe he won't," Cashman said. "All I can do is be guided by the professionals in the field of hip specialists. They say, 'Yes.'"
The news of Rodriguez's injury presents another challenge on the left side of the infield for the Yankees, who are already hoping 38-year-old shortstop Derek Jeter will recover from left ankle surgery in time to be in the Opening Day lineup.
"I'm not going to try to blow it off," Cashman said. "It's a significant blow. But we've dealt with significant blows, and hopefully, we'll be able to deal with this one as well."
Rodriguez, who will turn 38 in July, has $114 million remaining on a mega-deal that will take him through 2017 with the Yankees. He batted .272 with 18 home runs and 57 RBIs in 122 games for New York last season.
A third baseman was not thought to be on the Yankees' shopping list as the Winter Meetings started on Monday, with the club already expected to seek a starting catcher and a right fielder.
"We will wait for Alex," Cashman said. "We will cushion the blow. We will shore up every aspect that we possibly can."
In 2009, the Yankees got through the first month of the season with journeyman Cody Ransom holding down third base, and they'll be looking for help again this year, with Rodriguez potentially out for a longer period.
Veteran Eric Chavez is a free agent and could not be counted on for everyday duty this past season. The Yankees may also consider having Jayson Nix or Eduardo Nunez at third base on a limited basis.
"I can't tell you what our Opening Day situation is going to be there yet, but we have some more time to deal with that," Cashman said. "It's not an easy position to fill. We're going to get Alex back at some point, but other teams don't have a third baseman. The choices aren't pretty."