PHILADELPHIA -- Mookie Betts, Nolan Arenado, Kris Bryant and Francisco Lindor have not been traded, although momentum seems to be building for Betts to be shipped to the Dodgers or Padres. Until they are dealt, Phillies fans will keep asking -- why not them? Imagine how the Phillies’ 2020 prospects

PHILADELPHIA -- Mookie Betts, Nolan Arenado, Kris Bryant and Francisco Lindor have not been traded, although momentum seems to be building for Betts to be shipped to the Dodgers or Padres. Until they are dealt, Phillies fans will keep asking -- why not them?

Imagine how the Phillies’ 2020 prospects would improve with Bryant or Arenado at third base or Betts in center field? They would jump from arguably the fourth-best team in the National League East to arguably the favorite. But there are no indications the Phils are in serious pursuit to land any one of them before Opening Day. Things change, of course. A year ago at this time, the Phillies and Marlins were not talking about a J.T. Realmuto trade, but one text got the ball rolling and a few days later Philadelphia landed the best catcher in the Majors. Still, it is difficult to imagine that happening again.

Here is why:

Competitive Balance Tax

The Phillies are choosing to remain below the $208 million threshold, and Arenado, Bryant and Betts would push them past that. Arenado, who has seven years and $234 million (average annual value of $33.4 million) remaining on his contract with an opt-out clause after 2021, is the least likely option in the bunch. Fans can be heard yelling, "Who cares about the luxury tax? Why not just pay it and get the superstar?" Good point. But the Phils know they have a lot of concerns entering camp, and most of them center on pitching. It seems ownership wants to see how the team fares the first few months of the season. If everything clicks and the Phillies seem like legitimate postseason contenders, they likely will move past the luxury tax to acquire a top talent in July. But right now, they are uncomfortable pushing past that number with so many uncertainties.

The J.T. factor

The Phillies want to sign Realmuto to a multiyear contract extension, hopefully before Opening Day. If they acquire Arenado, Bryant or Betts, it would give them less financial flexibility to make the deal because they either would have to contend with Arenado’s contract or need to sign Betts or Bryant to an extension. A team can have only so many $100 million-plus players on the roster.

The Bohm factor

Quite simply, the Phillies need some of their top, young talent to step up at some point. It is why they are entering camp with Adam Haseley in center field. Third baseman Alec Bohm and right-hander Spencer Howard are the two best bets to follow Haseley into regular roles in 2020. Now, could Bohm stumble like Domonic Brown, who once was a can’t-miss prospect? Sure. But Bohm also could thrive and become the next Jimmy Rollins, Chase Utley or Ryan Howard. Many years ago, the Phillies had the opportunity to trade Utley to the A’s. They declined. Imagine if the Phils did not give Utley an opportunity to play?

The farm system

Internally, the Phillies believe they have the talent to get the Cubs, Red Sox or Rockies to listen. But how far can they go without crippling themselves in the future? Any trade almost certainly would start with Bohm and Howard. It might include Scott Kingery , too. Bryson Stott , whom the Phils selected in the first round of the Draft last summer, is highly regarded, but he does not have the professional track record of Bohm and Howard. The Phillies’ farm system ranks somewhere in the bottom half, perhaps around the bottom third. They could empty the cupboard, but they don’t think it’s a move worth making at the moment.

Todd Zolecki has covered the Phillies since 2003, and for MLB.com since 2009. Follow him on Twitter and Facebook .