There's a time to move on. To wish one another the best and promise to stay in touch. Even your favorite player will leave at some point. At this time of the year, there are the tough conversations happening in almost every front office.
When the Mariners traded lefty James Paxton to the Yankees for three prospects, it had nothing to do with how they felt about him. They love the guy. But this was a trade the Mariners believe will upgrade their farm system while providing some payroll flexibility. Ultimately, they believe they'll be better. As for the Yankees, they're all in for 2019.
This is the kind of deal that gives both teams what they want. And wouldn't it be nice to see more like them? Let's consider seven players who could be on the move for the similar reasons:
1. Zack Greinke, RHP, D-backs
The D-backs are in listening mode as they attempt to retool their roster. Sure, some teams are going to be scared off by Greinke's age (35) and contract (three more seasons at $105 million). The D-backs might have to pick up some of that money. But this would be a huge pickup because the guy can still pitch (last two seasons: 12th in MLB in FanGraphs WAR and xFIP; eighth in WHIP).

2. Whit Merrifield, 2B, Royals
This would be a reality-check trade for the Royals. But it has to be considered, given how much they could get in return. Merrifield is four seasons from free agency, can play all over the diamond and led the American League in hits and stolen bases in 2018 while posting a solid .367 OBP.

3. J.T. Realmuto, C, Marlins
This one appears to be a matter of when, not if, as the Marlins listen to offers for a 27-year-old catcher who might be the best in the game. However, the Marlins need to be careful about overplaying their hand. Realmuto is two years from free agency and reaching the point where the return will start to go down. The Marlins surely have gotten an accurate assessment of his value by now.

4. Corey Kluber, RHP, Indians
We'll find out how serious Cleveland is about retooling its roster with how the club handles discussions involving its ace. Even with some regression in 2018, he's still a top-of-the-rotation guy, having pitched at least 200 innings in each of the past five seasons, with a 2.85 ERA over that span. His contract is also management friendly.

5. Nicholas Castellanos, RF, Tigers
The Tigers may wish they'd moved Castellanos a year ago before he started to close in on his post-2019 free agency. His power has trended upward over the past three seasons, during which he's averaged a .495 slugging percentage.

6. Corey Dickerson, RF, Pirates
Few players helped themselves as much as Dickerson did in 2018 with a solid offensive season, plus Gold Glove play in right field. Like Castellanos, he's now just a year from free agency, so his value will vary from team to team.

7. Carlos Santana, 1B, Phillies
After a difficult first month, Santana had his usual numbers -- .364 OBP, .808 OPS and 22 home runs in 133 games -- and the Phillies are listening to offers. There aren't a lot of scenarios under which trading Santana seems like a smart move, though one possibility for Philadelphia is adding Bryce Harper while moving Rhys Hoskins to first base.