ENGLEWOOD, Colo. -- The sample size is just five games, but the Denver Broncos' season already has raised more than a question or two about how they will proceed as the schedule gets tougher in the coming weeks.

To this point, the Broncos have had a dominating performance against the Dallas Cowboys in Week 2 that had folks buzzing coast to coast about their postseason possibilities. But they've also had two wins that could have been dominating before mistakes turned them into nail-biters against the Los Angeles Chargers and Oakland Raiders.

Then they had a clunker -- their only road trip of the season to this point -- against the Buffalo Bills; a loss that was explained at least a little when the Bills defeated the Falcons in Atlanta the following week. But then came the home clunker against the New York Giants this past Sunday -- a loss-for-words defeat to a previously 0-5 team missing at least seven starters. The Broncos' performance cashed in much of the goodwill from the team's faithful that came with the three wins.

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"It was a big game for us," said Broncos coach Vance Joseph. "A chance to go 4-1. ... To [the Giants'] credit, they came in and played hard and played fast and had a great plan in all three phases. They won the football game. With that being said, it's early. It's a hard league."

The Broncos are about to find out how difficult the league can be and how ready they are for that challenge given their early-season inconsistencies. They play their next three on the road, starting Sunday against the Chargers, then against the Kansas City Chiefs, who lead the AFC West at 5-1, as well as the Philadelphia Eagles (5-1). They return home on Nov. 12 against the New England Patriots (4-2).

"We just have to clean things up," said running back C.J. Anderson. "There are some things I need to do to make sure I'm doing everything I can do. But we have to clean it up. We can't play like we did [Sunday]. We won't beat people we need to beat playing like that."

The last three matches have shown that Denver's opponents have studied how the Broncos won two games to open the season. The Bills and Giants have scored 23 and 26 points, respectively. Both of those offenses, though ranked near the bottom of the league this season, put together multiple sustained drives against the Broncos.

The Bills had 74- and 69-yard touchdown drives to go with a 16-play field goal drive. The Giants had a 13-play, 69-yard field goal drive on their first possession of the game to go with an 80-yard touchdown drive.

As opposing offenses have seen, gone are the days of the Broncos matching up their All-Pro cornerbacks on specific players in coverage. Chris Harris Jr. and Aqib Talib have largely lined up in the same spot in the defensive formation each week, playing at traditional right and left cornerback spots, respectively.

And while that is a safe bet much of the time with players of that caliber, it allowed the Giants to repeatedly isolate tight end Evan Engram against Broncos linebackers and safeties -- even though Engram was easily the most significant big-play threat the injury-ravaged Giants had at receiver.

"We had a great plan for [Engram] and didn't get it done," Joseph said. "We knew coming into that game that he was going to be their one option they had to work. It was going to be No. 88. We knew it. They knew it. Our players knew it and we didn't get it done."

The Broncos also have forced just four turnovers in six games -- only six teams in the league have four or fewer.

Denver has scored a touchdown just twice on 11 trips inside the red zone over the past three games. It managed just 42 (16, 16 and 10) points during that span, compared to the 66 it scored in the two wins to start the season.

Quarterback Trevor Siemian has six interceptions, including a game-crippling pick-six just before halftime on Sunday night, and has been sacked 17 times because of inconsistent play on the offensive line.

The 40-pass mark continues to be the topping point for the Broncos' offense and Siemian. With Sunday's loss, the team is now 1-6 in Siemian's starts when he throws 40 or more passes and 10-2 in starts he throws fewer than 40 passes.

"We have some big plays that we've missed and he's made some nice plays under pressure, it's half and half," Joseph said. "It hasn't been perfect, I won't lie and tell you that it's perfect. He understands that he has to play better in spots, we have to protect better in spots and we have to run the football better. That's our formula."