Richards plans to get a second opinion from Dr. James Andrews before deciding whether to have Tommy John surgery, but the Angels are preparing for the prolonged absence of their best starting pitcher. Richards was placed on the disabled list Friday before the Angels opened a six-game homestand.
"No doubt, it's disappointing to lose somebody who's so impactful," general manager Billy Eppler told The Associated Press in a phone interview. "We know that the schedule is unforgiving, but it's going to be a test for us going forward that we're going to attempt to meet as a team."
The Angels' rotation was the team's deepest area just six weeks ago, but four potential starters are now sidelined in various stages of recovery from arm injuries. Los Angeles already is without injured left-handers Andrew Heaney and C.J. Wilson, while Tyler Skaggs still hasn't returned from his own elbow ligament replacement surgery in August 2014.
The Angels don't need a fifth starter until May 14, and Eppler is looking for ways to fill the gaps.
"We have some time to process this and be relatively pragmatic," Eppler said, noting the difficulty of making major trades in May. "That causes you to test the depth you signed in the minor leagues, and to look at internal candidates."
The 27-year-old Richards made his first opening day start for the Angels last month, cementing his rise atop the staff since his breakthrough 2014 season. He is 1/3 with a 2.34 ERA in six starts this season, repeatedly facing other teams' aces and getting meager run support from his light-hitting teammates.
The hard-throwing right-hander already had been scratched from his scheduled start Friday with arm fatigue after throwing only four innings last week against Texas. Long reliever Cory Rasmus took his start against Tampa Bay.
"I think everybody was shocked, just like I was," Richards said before Friday's game. "I was still throwing kind of hard, despite having my arm being the way it is. I was shocked when I heard the news."
Yahoo! Sports first reported Richards' injury, and it was later confirmed by ESPN's Michael Eaves.
Heaney, the Angels' No. 2 starter to open the season, also has damage to an elbow ligament, but is attempting to treat the injury with a platelet-rich plasma injection earlier this week, followed by several weeks of rest.
"The standard of care is to allow the healing properties of that injection to work," said Eppler, noting that Heaney might not pick up a baseball for more than two months.
Richards went 13-4 with a 2.61 ERA in 2014 while often pitching spectacularly for the Angels, who finished with 98 wins and the majors' best regular-season record. But Richards needed season-ending knee surgery that August after getting hurt while covering first base, and Los Angeles didn't win a playoff game.
Richards then went 15-12 with a 3.65 ERA last season, emerging as a dependable No. 1 starter. He signed a one-year, $6.425 million deal for the current season to avoid arbitration, and he won't be eligible for free agency until the 2018 season.
The injury would be the biggest blow yet to the Angels' suddenly beleaguered rotation, which had been one of the few areas with depth for a franchise with a poorly regarded farm system.
"Hopefully we'll re-establish the depth," manager Mike Scioscia said. "Our challenge right now is to put guys out there that can give us opportunities to win games."
Wilson, who is making $20 million this season, has shoulder tendinitis that has kept the left-hander off the mound for nearly two months. The Angels don't know when he will return.
Skaggs had been pitching in the minors until he was shut down last week to recover from biceps tendinitis.
The Angels could recall right-hander Matt Shoemaker, who was sent to the minors last weekend after a poor April performance in their rotation. Eppler also mentioned left-hander Nate Smith, who has looked sharp in six starts for Triple-A Salt Lake this season.