Having a lineup of
1. Anthony Gose CF
2. Ruben Tejada SS
3. David Wright 3B
4. Ike Davis 1B
5. Lucas Duda RF
6. Daniel Murphy 2B
7. Travis D'Arnaud C
8. Jason Bay LF
Would set us back for years? How about no.
Winning teams build strong teams up the middle. P,C,SS,CF and have power on the corners. 1B/3B/RF/LF
With young Tejada at SS, young Gose in Center, young D'Arnaud behind the dish and Wright / Davis power on the corners with Niese and Wheeler in the rotation the Mets would be building their team much like the Baltimore Orioles.
Wieters (C) Machado (SS) Jones (CF) Chen/Bundy (P)
D'Arnaud (C) Tejada (SS) Gose (CF) Wheeler/Niese (P)
We would be set offensively long term with that core and you can always find good pitching.
(When Dickey,Niese,Wheeler are your core starters)