Jackson did not start Wednesday in the Cubs' series finale against the Padres. Cubs manager Dale Sveum wanted to give the 24-year-old a day to catch his breath.
"Surprised [at the strikeouts]? Yeah, at that rate," Sveum said Wednesday. "I'm not surprised he's had some strikeouts. We knew that was going to happen. We're learning a lot about him, and it's basically come down to swinging out of the strike zone. It's not like he's swinging through anything."
One thing Jackson doesn't lack is confidence. The Cubs' first-round Draft pick in 2009, Jackson has handled the at-bats well.
"It's nothing he hasn't gone through -- not at this level," Sveum said. "This was part of the reason why we called him up, too, to see first hand and get a good grip on what's going on."
What can Sveum do?
"You don't want him to go up every at-bat and change," Sveum said. "[Tuesday] night, he probably had four different hand positions and three different set-ups. Those are the things you have to try to stay away from and let these kids let their athleticism come out, too.
"He's a confident kid who knows there's something a little wrong or something he needs to change to move forward and understand this is big league pitching, and they're not going to give in," Sveum said. "He's willing to make adjustments to succeed here."