Myers sought a second opinion and will have the surgery on Thursday.
"This kid is special. This will be a big blow," Padres interim manager Pat Murphy said before Wednesday's game against the Athletics. "Everybody will have to step up."
Murphy was at Triple-A El Paso last week when Myers was rehabbing there.
"I saw a great player who was seemingly healthy," Murphy said. "He had it heavily taped."
Murphy said Myers will be able to start baseball-related activities again in eight weeks but he would not rule out a quicker recovery.
• Murphy has experience replacing long-tenured coaches, as he took over for Arizona State's legendary Jim Brock, who coached Barry Bonds among others, 20 years ago. "I'm very sensitive to change like that," Murphy said. "I learned from that situation."
• Catcher Derek Norris is playing his first game in Oakland since the Athletics traded him to the Padres. "It will definitely be different," he said. "Even coming into the parking lot was different."