While red zone efficiency is certainly one stat worth looking at, but I would not go so far as to proclaim that is so important that it is the difference between winning and losing in the NFL.
First, a look at some of the top ten Red-Zone offenses in the NFL in 2013.
3. Dallas (70.5%); currently 7-7, 10th in the NFC playoff picture
4. Detroit (61.2%); currently 7-6, 8th in the NFC
5. Oakland (59.5%); 4-10, 13th in the AFC, eliminated
8. Cleveland (58.1%); 4-10, 15th, eliminated
9. Tennessee (57.8%); 5-9, 11th, eliminated
Next, among the bottom five there are a pair of potential playoff teams:
31. Philadelphia (45.8%); 8-6, currently #3 seed in the NFC
28. Green Bay (49.1%); 7-6-1, a half-game off the NFC North lead
Now a look at some of the top Red Zone defenses:
2. Baltimore (39.4%); 7-6, currently in 7th in the AFC
3. Detroit (40.0%); a top-5 RZ team in both categories is 7-6
5. NY Jets (45.5%); 6-8, 10th, eliminated
6. Tampa Bay (45.5%); 4-10, 14th, eliminated
7. Buffalo (48.9%); 5-9, 12th, eliminated
9. St. Louis (52.7%); 6-8, 11th, eliminated
And among the worst red zone defenses are the #25 Colts (clinched a playoff spot), #26 Denver (#1 seed) and #27 San Diego (7-7, on the bubble one game behind Miami).
While I do agree that red zone play is important (and that it needs to improve for the Patriots), I would also suggest that it is not an absolute difference between winning and losing in the NFL.