Miami has swept (won 4:0) first two series (against New Jersey Nets and Washington Wizards) and therefore had a lot of time to rest.
Though the best Heat player so far is Dwayne Wade their main concern is Shaq's hip contusion which limits his abilities and caused him to miss 2 games against Wizards (it's still uncertain whether he'll be able to play in first game against Pistons.

Detroit eliminated 7th seeded Philadelphia 76ers in 5 games and then won against Indiana Pacers in 6 games.
Though they had some problems Pistons advanced to Eastern Conference Finals thanks to their suffocating defence that won them championship last year.

Gm 1: at MIA, Mon., May 23
Gm 2: at MIA, Wed., May 25
Gm 3: at DET, Sun., May 29
Gm 4: at DET, Tue., May 31
*Gm 5: at MIA, Thu., June 2
*Gm 6: at DET, Sat., June 4
*Gm 7: at MIA, Mon., June 6
(* if neccessary)