San Diego general manager Josh Byrnes said on Wednesday that Cashner -- who is an avid outdoorsman -- was injured by a companion when the two were dressing meat, a cut that caused a puncture wound to his thumb. The two were apparently trimming carcass with the intent of preserving the meat.
Cashner later had surgery on the thumb. Byrnes was told by doctors that Cashner will need a three-month recovery from the injury before he can start a throwing program.
"To say he'll be ready by Opening Day is not realistic," Byrnes said.
There was good news, though.
"The doctor didn't expect any long-term consequences," Byrnes said.
Cashner was 3-4 with a 4.27 ERA in 33 games last season for the Padres, including five starts. The Padres considered him to be a candidate to win a spot in the starting rotation next season.
That means the Padres, who figure they have eight healthy candidates for the rotation, will begin the regular season with pitchers Cory Luebke, Joe Wieland (both recovering from Tommy John surgery) and Cashner on the DL.
"That's not Plan A, but those guys will be back at some point," Byrnes said.
Cashner, 26, started the season as the Padres' eighth-inning specialist before moving into the rotation. But he went on the DL on July 4 with a strained lat. He returned in September and was shut down in the middle of the month after aggravating his lat injury.
However, Cashner returned to throw one scoreless inning on the final day of the regular season in Milwaukee.
On Monday, the Padres signed Jason Marquis to a one-year deal to give the club nine starting candidates. That number is now eight following Cashner's injury, though Byrnes said the plan is still to add one more starter.
To that end, the Padres had a "slightly busier" day Wednesday at the Winter Meetings as far as their discussions with teams and agents.
"But there's nothing too significant on the trade or free-agent front," Byrnes said.