The Denver Broncos' 6-1 start puts them among the league's elite. Their inability to score on their opening drive, however, places them among some dubious company.

The Broncos have been outscored 39-24 in the first quarter and they've trailed at halftime four straight weeks. They learned Sunday at Baltimore that they can't keep counting on their second-half surges to carry them.

Denver joins Oakland, Kansas City and Houston as the only teams not to score on their opening offensive possession yet this season, according to STATS LLC.

So, why has the Broncos offense sputtered out of the starting blocks?

Mistakes, poor play calls, bad protection -- the list is long.

(Copyright 2009 by The Associated Press. All Rights Reserved.)