Angels pitcher Garrett Richards undergoes stem-cell procedure on injured elbow

In 2010, right-hander Bartolo Colon traveled to his native Dominican Republic for an unusual procedure.

A doctor extracted fat and bone marrow, and reinjected the concentrated mix into Colon’s injured shoulder. Suddenly, Colon’s arm, and career, were rejuvenated.

The stem-cell therapy was controversial in 2010, but it has since gained increased acceptance among athletes, particularly pitchers.

“They all saw what happened to Colon,” said Joseph Purita, the Florida-based doctor who performed Colon’s procedure. “I mean, the guy’s still pitching at [42] years old. Just hit a home run a couple weeks ago.”

On Monday, Angels right-hander Garrett Richards became the highest-profile player since Colon to undergo a similar procedure, or at least acknowledge it publicly. Some fans might wonder: What? And: Why?

Richards sustained a high-grade tear of his ulnar collateral ligament in early May. Usually, that almost guarantees Tommy John surgery, which would sideline Richards for most, possibly all, of 2017.

If effective, the benefits of stem-cell therapy, then, are obvious.

Purita, who did not perform Richards’ procedure, said, “I’ve had some players that have gotten back in three months.”

The procedure is still new, and its potential for Richards, who has been unavailable to reporters since the procedure, is difficult to judge.

Most doctors use stem-cell therapy in conjunction with platelet-rich plasma (PRP) injections.

“Think of planting a garden,” Purita said. “The stem cells are the seeds. The fat tissue is the soil, and some seeds and some growth factors. And think of the PRP as fertilizer. That’s your analogy. Basically it’s planting a garden and watching it grow.”

If Richards’ arm bears fruit in six to eight weeks, he could return as early as August. If not, he’ll likely opt for surgery.

More injuries

The Angels relegated two more players to the disabled list on Tuesday: left fielder Daniel Nava and pitcher Cory Rasmus, both with groin injuries.

Eight players have now spent time on the disabled list — Nava twice. The Angels recalled outfielder Rafael Ortega and pitcher A.J. Achter from triple-A Salt Lake.

Nava injured his groin in the fifth inning on Monday. An MRI exam revealed a strain. Nava predicted his disabled list stint would be brief.

“It’s more frustrating than anything,” Nava said.

Rasmus tweaked his groin on May 12 against the St. Louis Cardinals, and the injury hasn’t improved.

“I don’t think it’ll be anything, but better safe than sorry,” Rasmus said.

Short hops

As of Tuesday evening, the Angels had not finalized their impending deal with free-agent pitcher Tim Lincecum. … C.J. Cron has yet to start in a National League park this season, and Tuesday was no different. Cron has been one of the Angels’ hottest players, with an on-base-plus-slugging percentage of over .900 in May, but Manager Mike Scioscia said Cron won’t start a National League game unless first baseman Albert Pujols needs a day off. “Albert’s the first baseman. There’s nowhere for me to play,” Cron said. “So you’ve got to be ready to help the team, and right now it’s pinch-hitting.”