"It is an honor for me to be here," Ynoa said. "I was here when I signed just one time to see the field. I feel happy to be back here and play against them."
On July 2, 2008, Ynoa signed for a $4.25 million bonus with the A's, then the highest bonus the team had ever given. The team flew him to Oakland to see the stadium shortly after, with Ynoa vividly remembering his first visit.
"I always remember, back in the day when they brought me here for the first time, they took me on the mound. I was looking and dreaming, all that stuff," Ynoa said.
Ynoa was highly regarded by the A's, but only pitched as high as Class A Advanced Stockton with the club. Injuries hampered him throughout his time with the A's, with Tommy John surgery requiring him to miss most of 2010 and all of 2011.
Oakland traded him to the White Sox on Dec. 9, 2014, along with right-hander Jeff Samardzija, for a package that included three current Major League players for the A's -- shortstop Marcus Semien, catcher Josh Phegley and right-hander Chris Bassitt.
"My wish was to play with Oakland, but something happened that you can't control and I'm here [with Chicago]," Ynoa said. "I thank the Oakland A's for giving me the opportunity to train me to get to the big leagues. Thanks to God first, but then to them and the White Sox, too."
Ynoa made his Major League debut June 14 last year for the White Sox and pitched once against the A's in 2016, giving up a run in one inning Aug. 19 in Chicago. He admitted he felt "butterflies in my stomach" when he faced the A's for the first time.
But for Ynoa, getting a chance to finally pitch in the Coliseum will be something he cherishes.
"I think it's going to be my wish for today, to get an opportunity to pitch here against my old team," Ynoa said. "It's going to be different -- I think it's going to be a little bit nervous. All the fans from here were helping me a lot through the surgery and everything. I think it's going to be a good three days here."
Alex Simon is a reporter for MLB.com and covered the White Sox on Monday. Follow him on Twitter at @alexsimon99.