CHICAGO -- During the final few days of the regular season, there was a realization among the Cubs players that a few notable nameplates might be missing from the clubhouse next year. A winter of change is coming and no one in the core group will be immune to trade rumors.

"I know there's some guys that might not be here that were key for us in the past years," Javier Báez said. "But you've got to understand, you've got to understand the business."

On Monday at Wrigley Field, Cubs president of baseball operations Theo Epstein made it clear that no players on the roster are deemed untouchable. There will be a new manager, as well as changes in the front-office structure, and it could be time to shake up a roster that has not lived up to the dynasty talk that existed before the team's four straight playoff berths.

That streak ended with a third-place finish in the National League Central this year and now Epstein and Co. are taking a hard look at the roster with 2020 and the future in mind.

"Looking back at this group that we won with," Epstein said, "I had this belief that this group of players that won the World Series at 22, 23 years old were going to grow into an unstoppable set of players, and we could continue to supplement them and show faith in them."

As that belief took hold, Epstein poured resources into the payroll and traded away prospect assets in the name of adding impact pieces around a young position-player core consisting of Báez, Kris Bryant, Willson Contreras, Anthony Rizzo and Kyle Schwarber. Now, Epstein might need to trade from that group for the sake of trying to construct the next World Series team.

Báez, Bryant, Rizzo and Schwarber will be eligible for free agency in 2022, if the Cubs pick up the next two team options on Rizzo's contract. Contreras will follow as a free agent in '23. This winter, expect Epstein to approach some of them about potential contract extensions. If no deal can be reached, then expect more trade talk to surface.

"Look, we're open to change. We're open-minded about this roster," Epstein said. "I expect to have a lot of trade discussions this winter. I think a lot of the players on this year's team are going to be part of the next Cubs championship team, so we want to be mindful of that, but it's also really hard to accomplish improvement and change in certain areas unless you're extremely open-minded.

"As we have in previous offseasons, I think we're very likely to engage certain players in discussions about long-term contracts and see if there's a way to extend players' windows as Cubs that way. And, if that's not possible, that might make you, as I said, open-minded about trades.

"There's more than one way to sort of take full advantage of a player's value. We're just going to balance those concerns going forward."

Worth noting

• Outfielder Nicholas Castellanos is among the Cubs' free agents this winter, and he has expressed an interest in returning to Chicago. The Cubs are also interested in discussing a new contract with the Scott Boras client, but Epstein realizes that Castellanos has earned the right to test the open market to capitalize on a breakout season.

"Man, I love everything about Nick Castellanos," Epstein said. "I love the way he plays the game and would love to have him back. It's obviously a more complicated issue than just, 'Would you love to have the guy back?' ... He knows that we'd love to have him back. He also knows it's not as simple as that."

• The Cubs have a considerable cast of players coming off the books as free agents, but the payroll projects to already have $140 million committed in '20 before factoring in arbitration players (a group headlined by Báez, Bryant, Contreras and Schwarber) and other payroll considerations. Epstein declined to go into detail on how high the payroll can go next year.

"We've come to realize that strategically it's best just not to talk about it," Epstesin said. "We get everything that we need from ownership and we'll continue to get everything we need from ownership."

• Epstein said one planned change for the player development structure will be to hire a director of pitching and a director of hitting, "to ensure that we are building these departments, teaching the game, evaluating players for where the game is now and where the game will be going, to make sure that we continue to be at the cutting edge."

• Epstein praised the vocal clubhouse leadership of veteran Daniel Descalso this season when it came to accountability and said the Cubs will be looking to add more leader types this offseason, if possible.

• Epstein said no teams have reached out yet to ask permission to interview general manager Jed Hoyer or senior vice president of player personnel Jason McLeod for any front-office openings.

• At the moment, no surgical procedures loom for any of the Cubs' players, according to Epstein.