As good as any but better than most
Oh, I'm sorry, I just assumed you followed the NFL.
In the past 5 years alone off the top of my head:
Jets (Rex Ryan)
49ers (Jim Harbaugh)
Falcons (Mike Smith) * Who started the same year as Sparano. Now compare the Falcons and Dolphins success.
Lions (Jim Shwartz)
Cowboys (Jason Garret)
These teams had poor records before being taken over. And if you tell me they had a QB and we need one too, well then, you might as well state that water is a liquid. All the great teams have good head coach/QB combos.