Rex hasn't guaranteed or bragged in so long. Probably before last year's Giants game when he said the Jets were the best team in NY. And no, "put some hot sauce on him" doesn't count.
Unfortunately, too many of us get brainwashed into thinking he guarantees a Super Bowl win every week. Well, he doesn't.
If you can't see that he's making an effort to keep his mouth shut and trying to learn from his mistakes, then you need to stop reading what ESPN or NFL network says and start reading the transcripts of his press conferences. You'll see he takes a less loud-mouth approach these days. Stop painting him still as sht-talking, loudmouth. he really hasn't done at all this season.