Want some recent history to explain those statistics?
Manning played against the #1, #2, #11, and #5 defenses since Christmas...
Grossman faced the #13 Saints, #19 Seahawks, and the #26 Packers. In fact, Rex hasn't faced a Top Twelve defense since November (adding the #29 Lions, #21 Buccaneers, #27 Rams, and the #14 Vikings)
Indy'd defense was ranked #22 for the regular season, but clearly their D has stepped up since the return of Bob Sanders, and with DT McFarland getting acclimated to his new team. They lost both starting DT's early this year to non-football injuries, and were playing our FIFTH string option, a rookie CB, at safety. Now that those huge gaps have been plugged, they're averaging 16 pts per playoff game, whch would put them at #4 in the NFL in the regular season. Going back to the MNF game vs Cincy, the D is averaging 19 ppg, which puts them at #8 in the NFL. Clearly, this isn't a 22nd ranked unit.
By the way, the Colts and Bears played 5 common opponents this year... with the Colts going 6-0 (beating the Patriots twice), and the Bears 3-2. (The Bears lost at Foxboro, and at home to the Dolphins. The Colts won with those settings.)