SANTA CLARA, Calif. -- If last week's opponent offered an unpleasant reminder for San Francisco 49ers quarterback Colin Kaepernick, this week's matchup should remind him of the good old days.

In 2015, Kaepernick had what he called the worst game of his career in Arizona, but he returned there last week and posted a much better performance. Now he faces an even tougher challenge against the team he made his fourth career start against, the New England Patriots.

"I remember being up a lot and having them come rushing back," Kaepernick said of that game played on Dec. 16, 2012. "It was a great feeling to go up there, get that victory, especially against a team like that. It was huge, and it was another confidence builder for our team, for myself at that point in time, that we were playing one of the best teams in the league and went there on the road ... and won. So, I think we have a similar opportunity this week to play a very good Patriots team and go out and get a victory."

"It's a constant evolution," said Colin Kaepernick. "It's a constant growth being able to become a better man." Ezra Shaw/Getty Images

In a way, Kaepernick announced his presence to the rest of the league that day in Foxborough, Massachusetts. He finished with 221 yards in the air, four touchdowns and an interception in an exciting 41-34 win.

Much has changed for Kaepernick both on and off the field.

After outdueling Tom Brady and the Patriots, Kaepernick's quick ascent to superstar status was matched only by how fast he fell. Along the way, Kaepernick earned a reputation for being surly and reclusive, regularly refusing to offer more than a few words when dealing with the media.

In the time since, Kaepernick has lost and regained the Niners starting quarterback job, gone through multiple surgeries, nearly been traded, renegotiated his contract and become one of the most polarizing figures in the country with his decision to kneel during the national anthem in protest of racial oppression and inequality.

Off the field, Kaepernick has become more approachable and outspoken, something he attributes to feeling more at home in his skin.

"I'm comfortable with everything that I'm saying, what I represent and who I am," Kaepernick said. "At that point in time, there was a situation where I didn't feel comfortable talking because I didn't want my words used against me, and now I know if I represent my words properly, what my stance is, who I am properly, that those words can't be used against me."

Kaepernick said the issues he now speaks out against weren't necessarily on his mind back then, but what he has observed in the years since have left him pondering the meaning of his words and his platform.

"It's just things that I've seen," Kaepernick said. "Watching what's happened, who's saying what, things like that. Those are things that as a young person -- 'OK, why am I going to speak on those?' And as I've gotten older, it's being able to be true to what I believe in, who I am, and regardless of how people want to take that, that's on them, that's not a reflection of who I am.

"It's a constant evolution. It's a constant growth, being able to become a better man."

The same is true of Kaepernick's pursuit of becoming a better player or at least one more reminiscent of the player he used to be. Although the 49ers have lost all four of Kaepernick's starts, he has made noticeable progress in the past two weeks as he has gotten closer to the physical condition he used to be in and grown more comfortable in coach Chip Kelly's offense.

Kaepernick didn't reveal his current weight but said he's close to the 225 pounds he used to carry. With knee, shoulder and thumb surgeries behind him, Kaepernick also said he feels like his speed and elusiveness as a runner are returning to form. He leads all regular starting quarterbacks with 7.13 yards per carry, which is the highest among all Niners and puts him on pace for a career high in that category.

"I'm feeling better and better every week," Kaepernick said. "I feel like I'm starting to get some of my wiggle back, some of the movement, starting to feel very comfortable with where my health is, how my body's moving, those things."

After Sunday's loss to the Cardinals, Kaepernick said he's also building a greater understanding of Kelly's offense. He said that when Kelly calls a play, he understands the reasoning behind the call as well as how it might be setting something else up for later in the game.

"As much as I'd like to think I can jump right back in and be 100 percent on top of my game, it was something that took a little bit to get into a rhythm, get comfortable with everything that's happening within the offense, and it's coming more and more every week that I feel comfortable with what's going on, why we're calling plays, how we're trying to get things done and being able to build on those," Kaepernick said.

Those details have been evident in Kaepernick's increased production the past two weeks. After posting a 66.2 passer rating his first two starts, that number has jumped to 96.8 in the past two weeks.

Of course, there's still plenty of work for Kaepernick to do. He has struggled mightily in the second half of games, completing just 38.4 percent of his passes for a rating of 51.6 in the final two quarters compared with 71.2 percent and 120.0 in the opening 30 minutes.

"He's improving with his reads," offensive coordinator Curtis Modkins said. "He's improving with handling the offense, getting us in and out of plays. He's done a good job of extending plays. I think he's getting his legs. He's strong. He's running when he needs to. But like I said, he has some work to do, just like myself and the rest of the guys. But he's improving."

In Kaepernick's estimation, that improvement is coming in more ways than one.