"It was just a matter of standing tall and not collapsing on my back side, which allows me to be more around the plate, and have a better angle on the ball," Jackson said on "The Waddle & Silvy Show" on ESPN 1000. "It wasn't like a major mechanical thing. It was something small, which normally it is.
"With position players or pitchers, it's normally something small, but it helps in a big way."
Jackson was coming off a four-game losing streak, and he yielded just one walk while striking out six.
"We're asking him to get better at throwing strikes, and getting ahead in the count," Cooper said Wednesday on "Chicago's GameNight" on ESPN 1000. "When he struggles, he's falling behind and walking guys. We want him to put more balls in play."
Sounds simple, just like the tweak Cooper made to Jackson's mechanics.
"That's what a good coach does," Jackson said. "His job isn't to reconstruct a pitcher's mechanics. A lot of times, it's small adjustments, and those minor adjustments help in a big way. That's what a good pitching coach does. They look at small things each person is doing.
"Each pitcher is different, so they don't have everybody doing the same thing. Everybody's mechanics are different, and they figure out what's going on in that one person's mechanics, and they tweak it a little bit. And a lot of times it works."
Cooper said he was anxious to see how Jackson would respond to a recent conversation the two had.
"I was real excited to get him and real excited to have the first sideline [discussion], where you start to work and talk about things," Cooper said. "I thought the sideline went well, and I was very anxious to see what that one sideline brought.
"The big thing about his mechanics is to stand tall. That really is the big thing. I saw some video. It's not hard to see people's flaws. The tough part is to fix the flaws. That's where the challenge is, and I do like challenges."