Tropeano was originally diagnosed with a medium- to high-grade tear on the ulnar collateral ligament in his right elbow on July 19, one day after lasting just two innings against the Texas Rangers before leaving with right elbow discomfort. He received a second opinion in New York last week that confirmed the diagnosis before opting for the surgery over a platelet-rich plasma shot or a stem-cell injection -- the route that Angels right-hander Garrett Richards is taking to try to avoid becoming the third Angels pitcher to have the procedure.
No date has been scheduled yet, as Tropeano is still selecting a doctor to perform the procedure, said Eppler.
Even if Richards comes back healthy for 2017, the club's projected rotation will be decimated by injuries and free agency losses. The only healthy pitchers with substantial Major League experience under contract for next season are Matt Shoemaker, Tyler Skaggs and Ricky Nolasco, who was acquired in a trade Monday. Others who could contend for spots would be left-hander Nate Smith and right-hander Alex Meyer, who are both at Triple-A Salt Lake and ranked the club's Nos. 5 and 12 top prospects, respectively.
"You look at Garrett, you look at Heaney, you look at Nick Tropeano and that's a pretty good foundation for a rotation," Angels manager Mike Scioscia said. "It looks like we're most likely losing two of those guys, so there's a focus on Garrett and getting him back so we can rebuild our rotation."
Tropeano had the best ERA of anyone in the Angels' rotation at the time of his injury, finishing his season at 3-2 with a 3.56 ERA in 13 starts.
Cron ahead of schedule
Angels first baseman C.J. Cron took dry swings on Tuesday and will begin hitting in Arizona when the team leaves after Thursday's home series finale against Oakland. Cron had surgery on his fractured left hand on July 12 and was originally given a six-to-eight week recovery timetable.
"It's great," Scioscia said. "We're at three weeks, and you're seeing a guy who's swinging a bat. That's remarkable, and he feels good, so hopefully we're going to continue to get good news as he moves forward."
• Meyer, who has not pitched since May 3 with a right shoulder strain, threw a bullpen session in Arizona on Tuesday and will hopefully begin throwing in games next week, Scioscia said. Meyer was acquired along with Nolasco in Monday's trade that sent left-hander Hector Santiago to the Twins.
• Angels catcher Geovany Soto (left knee inflammation) has been able to squat and take part in all baseball activates, and will begin a rehab assignment with Triple-A Salt Lake on Thursday. Scioscia said he projects a five-to-seven day minimum for the assignment, saying he needs to make sure Soto gets used to catching on consecutive days before being activated.
Fabian Ardaya is a reporter for MLB.com based in Anaheim.