The Denver Broncos suddenly are looking fragile. They need to end their November swoon quickly or even could face the possibility of not playing in January.Peyton Manning and the defending AFC champions played their two worst games in the past three weeks, falling at New England at St. Louis.On Sunday, they take on a Miami team that is 6-4, winning four of its past five, with the loss coming at Detroit in the final seconds.Yes, the Dolphins’ resume of late is more impressive than the Broncos’.“I think there definitely is a sense of urgency,” Manning says. I think when you lose a game, what we’ve talked about offensively this week is everybody focuses on doing their job better, and you hope that results in better offensive play.”The Broncos (7-3) were held to seven points by the Rams; Manning usually can produce one touchdown in his sleep.“We’re not happy about last week’s game by any means with the way we played offensively, and we certainly want to play better,” Manning adds.