Cleveland Browns quarterback Baker Mayfield walks on the sideline in the second half of an NFL football game against the New England Patriots, Sunday, Oct. 27, 2019, in Foxborough, Mass. (AP Photo/Steven Senne)

DENVER | The Cleveland Browns were a trendy playoff pick with a star-stacked roster seemingly primed to end the NFL’s longest postseason drought. The Denver Broncos finally had an experienced quarterback to brighten their future.

The Browns (2-5) and Broncos (2-6) remain mired in the muck, however, and the frustration is boiling over.

Baker Mayfield had a locker room blowup and Joe Flacco ripped his coaches for being fraidy-cats a day before he was diagnosed with a neck injury that will sideline him Sunday when 27-year-old backup Brandon Allen makes his first NFL start.

Known for his outbursts on the field, Mayfield had a minor meltdown during his weekly media availability, abruptly storming away after taking offense to a line of questioning and later writing on Twitter that he’s frustrated by the mounting losses.

Baker’s subpar play through a difficult stretch has led to speculation about whether the 2018 first overall draft pick really is the Browns’ long-term answer at quarterback. He’s tied for the league lead with 12 interceptions and has just six touchdown throws after setting the NFL rookie record with 27 last year.

“I don’t know what it is, I really don’t,” Broncos pass rusher Von Miller said. “It’s the same offense. He had so much success last year. He’s got better weapons this year.”

Yet, the Browns are teetering on irrelevancy for a 17th consecutive season and rookie head coach Freddie Kitchens gave a lukewarm assessment of his young QB ahead of the team’s trip to Denver, where the Broncos had been living in what Emmanuel Sanders labeled “the world of suck” before the 49ers threw him a lifeline via trade two weeks ago.

The Broncos expected better things this season under Flacco, but their offense remains dysfunctional behind a penalty-plagued O-line and with Flacco sidelined, they don’t have a single QB who has taken an NFL snap.

Beaten down by 26 sacks and downbeat over a third last-minute loss last week, Flacco ripped offensive coordinator Rich Scangarello’s conservative play-calling after the Broncos lost a tough one at Indianapolis.

GM John Elway, head coach Vic Fangio and Scangarello all framed Flacco’s criticism as remarks regrettably made in the heat of the moment. Scangarello, a first-time offensive coordinator, also dismissed the notion he should get more aggressive, saying, “I think that the offense needs to do what it needs to do every week to win.”

With a herniated disk in his neck sidelining him six weeks minimum, the Broncos turn to Allen, a fourth-year pro from Arkansas who will make his first start since Jan. 2, 2016, against Kansas State in the Liberty Bowl.

“You can’t take anybody for granted in this league,” Browns cornerback T.J. Carrie said. “Definitely we’ll take a dive into the film.”

Old Razorbacks film.

Kitchens’ staff dug up Allen’s college games to learn more about this man of such mystery that even his own teammates couldn’t provide a scouting report.

“Honestly, I haven’t had too much work with him,” conceded Broncos wideout Courtland Sutton.

Other subplots Sunday in Denver, where the Browns eked out a 17-16 win last year:

MORE MOBILITY

One thing about Allen that’s a certainty is he’s much more mobile than Flacco.

“He does have a good feel in the pocket and he can go off-schedule,” Scangarello said, “so we’re excited about that element of his game.”

LOCK DOWN

Broncos fans want to see rookie QB Drew Lock get his shot, but general manager John Elway said the second-round draft pick from Missouri won’t return from IR until Week 11 following the team’s bye. Lock sprained his right thumb in the preseason and hasn’t practiced since Aug. 16.

Allen’s backup will be Brett Rypien, an undrafted rookie from Boise State promoted from the practice squad.

FLAG FOOTBALL

The Browns lead the league with 70 penalties, putting them on pace for 160, just three shy of the NFL record set by the 2011 Raiders. So, Kitchens has resumed punishing players in practice by making them run when they draw flags just as he did during training camp.

“We were trying to keep the legs fresh,” guard Joel Bitonio said. “But, hey, we’ve got to figure out a way to stop …”

AWESOME AGGIES

Miller has always been a big fan of fellow Texas A&M alum Myles Garrett.

“He’s a superstar, been like that since Day 1,” Miller said. “He’s an Aggie legend. He’s been unstoppable this year. He’s got 10 sacks, just been killing tackles left and right side, he’s been doing a great job this year, playing the run, rushing the passer.”

Miller is off to a slow start statistically with just four sacks.

LABOR PEACE

Broncos CB Chris Harris Jr . said he won’t miss Sunday’s game even if his wife, Leah, is in labor.

“No, I’ll be good,” said Harris. “I think she can make it. My wife is a pro just like me. So, she knows. She’ll be able to figure it out, hopefully.”

This will be the couple’s fourth daughter.

“I’ve almost got a whole basketball team ready,” Harris said.

AP Sports Writer Tom Withers in Cleveland contributed.