ANAHEIM, Calif. -- Dillon Overton was charting pitches from the stands for Triple-A Nashville when he started getting multiple text messages.

Friends and family were reading reports that Overton might be called up to pitch Saturday's game for the Oakland A's and they wanted to know if the rumors were true.

Not long after, Overton got the news that he would be making the start Saturday against the Los Angeles Angels, making his major league debut. He immediately called his family to let them know.

"When I called, my mom started crying and asked if I was excited," Overton told the San Francisco Chronicle. "I said, 'Well of course I'm excited, mom, I'm going to the big leagues!'"

Because the A's starting pitchers have struggled so much, he finds himself in a situation the A's have already experienced twice this season. Overton will be the third starting pitcher to make his major league debut, joining Sean Manaea and Daniel Mengden.

Overton certainly earned it, going 8-4 with a 3.01 ERA in 14 games (13 starts) for Nashville, and he's been especially good lately -- he is 7-0 with a 1.40 ERA in his last seven starts.

"Our guys are telling us that he's really pitching well and he's come a long way," A's manager Bob Melvin told reporters after Thursday's game. "He's got a complement of pitches that gets him through righties and lefties both. We were impressed with what he did this spring. He's just continued to develop."

"We're at a point now where not only have we had some injuries and we've been using some guys, this is a guy that we like. He's healthy finally now and pitching well and you like to get a guy here when he's pitching well."

"Healthy now" is a big deal for Overton, who was drafted in the second round by the A's in 2013 but had to have Tommy John surgery before he could make his professional debut. Once healthy, he rose swiftly through the minor league system.

He'll be opposed by Angels right-hander Jhoulys Chacin, who could lose his spot in the starting rotation with another bad performance. In his last four starts, Chacin has an ERA of 8.83 (17 ER in 17 1/3 IP).

And while the Angels traded for Chacin on May 11 in a deal with the Braves to fill a slot in the rotation, they have a little more depth now that Nick Tropeano has returned from a sore shoulder.

The Angels optioned Tropeano to Triple-A Salt Lake Friday after completing a minor league rehab assignment even though Tropeano is the only Angels starter with a winning record (3-2) and has an ERA of 3.25, better than anyone currently in the rotation.

"Right now at this point in time, we're going to go with these five guys," Angels manager Mike Scioscia said.

The Angels could not send Chacin down to the minors without first designating him for assignment and passing him through waivers. But they could move him to the bullpen and make him a long reliever.