Overton, Oakland's No. 9 prospect, will have his contract selected from Triple-A Nashville on Saturday, when the left-hander will become the third A's pitcher this year to start in his MLB debut.
The A's will need to make a move to free up space for Overton on the 40-man roster.
The A's have six pitchers on the disabled list and needed a fifth starter for Saturday's game. Overton found out on Thursday that he would be coming up to the big leagues. He was charting pitches at a Triple-A game when he got the news, then made a phone call to his parents, Pat and Lavon.
"When I called them, my mom started crying and asked if I was excited and I said, 'Well of course I'm excited, Mom, I'm going to the big leagues'," Overton explained. "But no, they were extremely happy and happy for me and they couldn't be more happy."
Overton expects about 28 friends and family to attend his debut, including his wife Morgan. "It's going to be a good turnout," he said.
A second-round pick in the 2013, Draft, Overton has been pitching well of late with the Sounds, going 7-0 with a 1.40 ERA over his last seven starts. He has not allowed an earned run in his last three outings.
"I was trying to throw well enough to where I was making the people in the front office think about it for a minute and I've been blessed enough to throw good and they ended up giving me a call," said Overton, who added a cutter to his repertoire this year.
Overton will be the first player from Oakland's 2013 Draft class to make it to the Majors. Not bad for a pitcher who missed his first professional season after undergoing Tommy John surgery.
"I've been extremely blessed to be able to move as quick as I have," Overton said. "I had Tommy John surgery just three years ago. So to be able to move as quickly as I have, throw as well as I have, I've been extremely blessed and happy with how it's progressed."