Jackson wrote own script in second start

MESA, Ariz. -- Edwin Jackson decided to only throw fastballs on Friday, and apparently didn't tell Cubs pitching coach Chris Bosio or manager Rick Renteria, who planned to chat with the pitcher to figure out what happened.

"He threw 50 pitches, 50 fastballs," Renteria said Saturday. "He wanted to work on his fastball."

Making his second spring start, Jackson gave up three runs on four hits in his three innings of work against the Indians.

"I think maybe, as we talk about fastball command, maybe he was thinking, 'I'm going to try to hit the spots,'" Renteria said. "He got into a little trouble yesterday, and he had some elevated pitches and some pulled pitches. I think you have to kind of allow some flexibility in what he's trying to do. In his mind's eye, he had a particular idea of what he wanted to do and he did it for three innings."

Was Renteria surprised at Jackson's game plan?

"I saw a lot of fastballs," Renteria said. "I'll just say that I noticed it."

Jackson is in the second year of his four-year contract with the Cubs, and coming off a season in which he led the National League with 18 losses. Renteria didn't seem bothered by the pitcher's improvisation.

"I'll probably talk to him and have a conversation and clarify what the process was," Renteria said. "That doesn't hurt."