Change is coming to the Cubs roster, but that change should not extend to Kyle Schwarber.

The case for trading Schwarber makes sense: It would be selling at potentially the height of his value. It could also free up a corner outfield spot and subsequent money to bring back fan favorite Nicholas Castellanos (it would be hard to fit both Schwarber and Castellanos on the roster long-term).

But consider this: Schwarber performed almost as well as Castellanos down the stretch last season, putting up a .997 OPS after the All-Star Break compared to Castellanos' 1.002 OPS following the trade from the Tigers. Those totals were good for seventh and eighth in the National League in the second half.

Schwarber also ranked 11th in the NL in wRC+ (151) in the second half, just behind Castellanos and Anthony Rizzo. That led to a number of career highs for Schwarber this season, including homers (38), RBI (92), batting average (.250), slugging percentage (.531), OPS (.871) and doubles (29).

Chalk it up to a small sample all you want, but this is nearly half a season (257 plate appearances) where Schwarber was one of the best hitters in the league and it certainly seems like the 26-year-old finally reached his potential.

"There were obviously a lot of ups and downs [this season], but pretty pleased by how I handled it," Schwarber said during the last series of the year in St. Louis. "Overall, on a personal side there, it was definitely a positive."

Schwarber wouldn't completely acknowledge that something "clicked" in his second half, instead crediting his mindset and how he avoided riding the roller coaster of getting too high or low after each game.

The mindset also carried over into his approach at the plate, where he stopped trying to pull the ball so much and went to the opposite field more than ever before.

"I'm a pretty simple human," Schwarber said with a laugh. "Obviously whenever the ball is pitched away, you want to hit it that way. There's gonna be sometimes, too, when you catch it a little deep on the inside part of the plate and it goes that way and it lands in there for a hit.

"This game's really messed up because you can do everything right and get out and then you can do everything wrong and get a hit. You just gotta be able to stay consistent with the work and obviously some adjustments there with being able to stick more middle, it allows you to be a little more reactive away."

Sure seems like something clicked there mentally for Schwarber and the physical tools have always been there.

The development in the mental game has led to tangible changes on the stat sheet that very well might hold up over time. For example, Schwarber hit the ball on the ground less in 2019 than ever before and subsequently increased his line drive percentage. He also hit the ball harder overall, dipping to a career-best 12.7 percent low contact rate.

He silenced some of the doubters about his ability to make an impact against left-handed pitching, posting an .809 OPS against southpaws in the second half and carving out consistent playing time down the stretch regardless of the opposing pitcher.

It all adds up to a true breakout and Schwarber might just be scratching the surface of what he's fully capable of.

"I think he made some adjustments," Theo Epstein said on ESPN radio in an interview with David Kaplan and Pat Boyle last week. "Some of it was mindset and belief and approach and some of it was a little bit fundamental mechanics of the swing. But just the combination led to a really confident hitter up there who's dictating a little bit more instead of being reactive — not trying to cover every single hole, but going up there with a really good gameplan.

"More of the rhythm and timing to his swing — the prepitch movement that is a little bit unconventional, but it allowed him to always be on time as an amateur and as a minor-league player. When he's locked in like that and feeling good and has the right kind of approach, he's extremely dangerous. I think it just gets back to what we talk about with development not being linear in baseball — you never know when it's gonna click. A lot of guys have to go up and back — Triple-A to the big leagues a couple different times and in Kyle's case, he missed a whole year [due to injury]. He had that one really rough season initially in the leadoff spot and then had to go back to the minor leagues.

"I think he's reached that point where he's turned the corner and can be really impactful middle-of-the-order bat for years to come."

It can be dangerous to point to one half season for any player and extrapolate it out over a full campaign year over year, but if fans are really sold on bringing back Castellanos after two good months, why sell off Schwarber right now after he was essentially as effective as Castellanos over the same stretch?

Schwarber is also a lot more affordable than most other players capable of approaching 40 homers, as he's projected for $8 million by MLB Trade Rumors in 2020, his second year of arbitration.

It's unknown exactly what Schwarber would fetch in a trade because of the public perception about his defense, the lack of track record and how this Cubs front office views him. It's hard to see any team truly meeting the price Epstein and Co. will set forth given how highly they think of him internally.

So you have a left-handed slugger who tears up right-handed pitching and has started to come around against southpaws, a guy who could hit in the middle of the order, is still young (he'll turn 27 in March), affordable and may not fetch enough in a trade to make it worthwhile?

That doesn't exactly portend a trade coming this offseason involving Schwarber. If they held on to him this long, why deal him away now that he finally put it all together?

Sure, crazier things have happened and maybe some team meets the Cubs' asking price.

In the meantime, Schwarber will spend the winter making sure all those positive developments he made in the second half stick.

"The foundation's there," he said. "It's just being able to stay consistent. Whenever you pick up that bat again and start swinging, you got your routine, you got your standards for what you want to do with the ball and keep repeating it."