Fangraphs Depth Charts has the Phillies at 35.9 fWAR currently, including Wheeler and Didi. That puts us fourth in the division behind the Mets (42.6), Nationals (41) and Braves (40.3).
https://www.fangraphs.com/depthcharts.aspx?position=ALL&teamid=26
For reference they have Houston at 53.8 and the Yankees at 51.6 (including Cole).
Their rankings put us 7th in the NL as currently constructed and missing the wild card by 5.1 wins. Obviously its just one ranking and there are lots of moves to be made by other teams, so its not just those 5 wins that need to be made up, but I think its not unrealistic to think we could make up a lot of those within the roster before making any further moves.
They are predicting 2.9 wins combined between Eflin, VV and Pivetta. With a new pitching coach its not unrealstic to hope for a minor breakout for just one of those as a starter in 2020. Lets add 1 win there.
Scott Kingery put up 2.7 wins in 2019, they are predicting just 1 win for him in 2020. That seems very pessimistic barring injury. Lets add 1 more win there.
Adam Hasley put up 0.9 wins in 242 PAs in 2019. They are expecting 0.4 from just 249 in 2020. They assume Odúbel gets the bulk of the starts in Center, with Kinger and Quinn chipping in as well. I'm going to assume we don't see Herrera in red pinstripes again, and that either Hasely gets the bulk or another player from outside the org does. I'm going to say we get about 1.5 wins from Haseley or his replacement, which is a net +0.5 wins after taking out Odúbel.
Finally theres Cutch. He was fantastic in 2019 before his injury. Hes a year older and we don't know how the injury will affect him. They have him at 2.1 wins. That doesn't seem unfair, but Its not unreasonable to see him put up 3 wins either. He was on course for close to 4 wins if he had stayed healthy and played 150-160 games last year. Lets be cautious and round down to 2.5 wins, for +0.4 wins total.
There are other potential bounceback candidates but I think predicting more than Fangraphs has for Segura (2.3), Hoskins (3) and Gregorious (2.2) is overly optimistic.
Thats not an unrealistic path to an additional 2.9 wins, which still leaves us in fourth, though within striking distance, and assumes that we lose no wins to injury, or no additional signings by our division rivals. It only moves us up one place in the NL. We realistically need all of that to go at least that well, and find another 3-5 wins from somewhere else, either through even better improvement from what we already have, or through players outside the organisation.
If they were willing to go above the Lux tax limit then there are Free Agent solutions in positions of need, in Rendon (5.6), Donaldson (4.2), Ozuna (3.2), Ryu (2.9) and Keuchel (2.7).
Failing that, its trade or bust I feel.
NL Rankings
1. Dodgers: 49.7,
2. Mets: 42.6
3. Nationals 41.0
4. Braves 40.3
5. Cubs 40.2
6. Padres 38.2
7. Phillies 35.9
8. Cardinals 35.7
9. Diamondbacks 32.9
10. Brewers 32.2
11. Reds 32.2
12. Pirates 30.1
13. Rockies 28
14. Giants 24.4
15. Marlins 21.0
