OAKLAND, Calif. -- There is nothing quite like one last trip to the Oakland-Alameda County Coliseum to deflate the optimism of summer, as the mistake-prone Denver Broncos wobbled early, stumbled later and couldn't rebound in a season-opening 24-16 loss to the Oakland Raiders.

First-year coach Vic Fangio certainly passed the offseason test, as he seemed to settle the Broncos down after back-to-back seasons of double-digit losses, but his debut didn't go as Denver had hoped. The Raiders scored on a 10-play drive on their first possession of the game and never trailed.

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Troubling trend: Depth was the biggest concern hovering around the Broncos throughout the offseason, especially since the 2016 and 2017 drafts continued to leave fairly glaring holes. When cornerback Bryce Callahan didn't play because of a foot injury, it pushed Isaac Yiadom into the starting lineup. Raiders coach Jon Gruden consistently targeted Yiadom in the first half, including on Oakland's first touchdown and a 43-yard completion during the Raiders' second touchdown drive. Right tackle Ja'Wuan James, whom the Broncos made the highest-paid tackle in the league when they signed him in March, left the game in the first quarter with a knee injury, and that propelled Elijah Wilkinson into the lineup. Wilkinson is the Broncos' backup at both tackle spots and has been the leading backup at both guard spots in practice.

Biggest hole in the game plan: The running game early. This is the foundation of the offense, and while nobody is saying they should bust out the veer, the Broncos moved the ball far more effectively in the second half, when they committed to the run. They ran just seven times in the first half and never really looked in sync. They gained 73 yards on their first nine carries of the second half.

QB breakdown: Offensive line coach Mike Munchak was likely the most important acquisition this past offseason, given the Broncos' need to improve that group to get the most out of 34-year-old quarterback Joe Flacco. Flacco was smooth and consistently delivered the ball when the Broncos kept his front porch clean. But when things broke down in the middle of the line, he had difficulty escaping.

Pivotal play: With just under four minutes to play in the third quarter, the Broncos were in a third-down situation at the Raiders' 7-yard line. They trailed 14-3 at the time and had put together a physical, defense-pounding drive that had them poised to get right back in it. Flacco found DaeSean Hamilton in the end zone for what would have been a much-needed, momentum-awarding touchdown, but Hamilton dropped the well-placed ball.

Silver lining: In the past two seasons, a quick 14-0 lead by the Broncos' opponent would have turned into a rout of the ugliest proportions. Plus, although they didn't unpack the best of efforts in their first road game, the Broncos did show some resilience in the second half.