"There's no specific age or time," Jackson said. "The player will let you know when he's ready or when he's not. Nowadays, I think you've got guys all over the league on all different teams coming up 19, 20 [years old] and having success.
"I don't think there's one particular formula that works," he said. "It's different for every person. One thing for sure, you find out, the game will tell if they're ready or not."
Bryant's been on the fast track since he was selected second overall in last year's First-Year Player Draft. He played for short-season Boise, then was bumped up to Class A Advanced Daytona and finished in the Arizona Fall League. Now, he's in the big league camp. Top prospect Javier Baez also has two home runs this spring. Bryant is 22; Baez 21.
Jackson had appeared in 58 games before he made his big league debut. He did pitch again in the Minor Leagues from 2004-06. Did he get the call too soon?
"Who knows? I think [there's different opinions]," Jackson said. "You could say I was, you could say I wasn't. It made me a stronger person because I learned how to deal with adversity at a younger age. I think it made me stronger.
"It's tough to go out and learn how to deal with failure," he said. "I guess I had the luxury of when I did learn how to deal with failure is that it was at the big league level. I went through the Minor Leagues without struggling, so most of my struggles came in front of a television [audience]. It definitely makes you a stronger person. It molded me into the person I am today and to feel like whatever happens, I can make it through it."
On Friday, Jackson said he threw only fastballs against the Indians because that's all he wanted to work on. If other pitchers are doing the same and using Cactus League games to experiment, is Spring Training a fair gauge of a player's talent?
"They still have to hit it whether you're working on your fastball or not," Jackson said. "These guys are young, they're agile, they're flexible, they're strong and they're getting the bat through the zone. It's hard to say just because he's hitting or not hitting now that he won't be hitting or will be hitting down the road.
"Baseball's a crazy game, and you just never know," he said. "You see people have poor Spring Trainings and then once the season starts, they catch on fire. ... It's just a crazy game we play, and you never know about one particular person."