"I think he's right on schedule," Jackson said Tuesday.
"The pace has been a little bit slower than I've really wanted," Mayfield said.
Mayfield said that despite working with the second team during Tuesday's practice, which was open to the media. Both Mayfield and Jackson downplayed that, saying it was just a chance for Mayfield to work with some different teammates.
The varied evaluations come from point of view. Jackson said Mayfield is learning the NFL game while Tyrod Taylor, the starter, gets all the first-team reps.
"The game's not too big for [Mayfield]," Jackson said. "He demonstrates the ability to throw the ball and make decisions with the ball in his hands and [in] learning our system. I think he's on schedule.
"But is he a finished product? No. He's not supposed to be, either."
In that regard, Jackson emphasized that he likes what he sees of Taylor and that the team feels good knowing he is the starter. But the coach did say that Mayfield has improved noticeably taking snaps under center, something he did not have to do a lot in college.
Mayfield's self-assessment came from a competitor, someone who wants to play as soon as he can.
"There's always a learning curve," he said. "There's always bumps in the road. It's not going to be perfect, that's for sure. When you learn a new offense and you're going up against the best competition possible, yeah, there's going to be a learning curve."
He emphasized incremental improvement, saying "you're not going to complete the whole puzzle at once."
In Tuesday's work, Mayfield's best throw was a quick one down the seam to tight end Darren Fells in a two-minute situation. He also dropped a nice pass into David Njoku's hands at the goal line, only to see Njoku not hold on.
Jackson said the decision to give Mayfield second-team reps this week was to give him a different look with different players.
"I want to keep tinkering with it a little bit and I made the decision this week with the staff to make him second and get some reps there," Jackson said. "Nobody should read anything into it."
The Browns traded for Taylor in the offseason to start. In previous practices open to the media, free-agent signee Drew Stanton was the backup. Mayfield will be given the chance to earn his spot, but Stanton would no doubt be No. 2 if the Browns were playing a game. Jackson said Mayfield got the same number of practice reps at third team that he did at second.
"I have to be ready for whenever that opportunity comes, if that's this year, next year or in five years," Mayfield said. "I have to be ready as soon as that comes, and right now, getting better every day. That's all I can do."