Signed by Oakland for $4.25 million when he was 16, Ynoa has been limited to 17 professional games because of elbow problems.
Now on the 40-man roster of the A's, the 21-year-old right-hander reported to spring training Thursday after missing the opening week because of chicken pox.
"For one week it was bad," Ynoa said.
Given his 6-foot-7 height, Ynoa caught the attention of A's manager Bob Melvin.
"I didn't realize he was that size," Melvin said. "He could probably reach out and drop the ball in the catcher's mitt. I'm looking forward to watching him pitch. Everybody says he's pretty special when he's healthy."
Ynoa has yet to go through a full season. He started his career on the disabled list with the A's affiliate in the Arizona Rookie League due to a strained right elbow and he missed the entire season.
He made three starts in 2010 before more elbow problems and had surgery that August to reconstruct his ulnar collateral ligament.
Ynoa returned to the mound last June and made a combined 12 starts and two relief appearances for the Arizona League A's and Vermont of the Class-A New York-Penn League, going 1-4 with a 6.45 ERA and 25 strikeouts in 30 2-3 innings. He is working on a cutter, a pitch that intrigued him when he saw it during televised games while he was sidelined.
"I feel great mentally and now I am ready to do my best and just keep going," Ynoa said. "I'm OK with everything."
There are no restrictions on him, and Melvin expected Ynoa to be ready to appear in a game in two weeks.
"It's just like any other pitcher in spring training," Melvin said. "He's just a little behind."
Ynoa said he played catch a few days ago and feels normal.
"I lost a week," he said. "I just need to work hard on things I need to work on."
A's strength and conditioning coach Michael Henriques introduced yoga into warmups with players who arrived early in camp and it has caught on, with pitchers using it regularly. Melvin went through his first yoga stretch Thursday. "Everybody enjoys it," he said. ... RHP Jesse Chavez is to start Saturday's exhibition opener against Milwaukee. LHP Travis Blackley is to start Sunday and LHP Andrew Werner on Monday. ... RHP Jarrod Parker, LHP Sean Doolittle, LHP Jerry Blevins and RHP Ryan Cook each threw batting practice for the first time. ... The Arizona Diamondbacks used the A's minor league facility at Papago Park for a scrimmage. The fields at Salt River were soaked after being covered in snow Wednesday.