Hughes will be OK. Kennedy, probably not so much. However, if you've got a starting rotation of Sabathia, Wang, Burnett, Pettitte and Hughes, I think that will do nicely. Then have Joba for Innings 7 and/or 8 and Mo for 9.
I REALLY hope Hughes will be ok. But he's only showed 2 signs of that to me (his no-hitter in Texas and against the Indians in the playoffs when he came in for relief for Roger Clemens).
As for our bullpen, it's really not that bad. Have you forgotten Brian Bruney and Phil Coke already? Here are their numbers compared to Joba's from just the bullpen:
Brian Bruney 32 games, 34.1 IP, 18 hits, 7 runs, 7 ER, 2 HR, 16 BB, 33 SO, 3-0 with 1 SV and a 1.84 ERA
Joba Chamberlain 30 games, 35 IP, 27 hits, 9 runs, 9 ER, 1 HR, 14 BB, 44 SO, 1-2 with 0 SV and a 2.31 ERA
Phil Coke 12 games, 14.2 IP, 8 hits, 1 run, 1 ER, 0 HR, 2 BB, 14 SO, 1-0 with 0 SV and a 0.61 ERA
The biggest discrepancy between Joba's and Bruney's numbers are Joba has more strikeouts but Bruney has a lower ERA in 2 more games but almost an inning of work less.