Officially, Allen was a practice-squad quarterback. Unofficially, he was the emergency pandemic quarterback, whose primary task was just being available. Because of COVID-19, even the threat of a positive test can temporarily wipe out a team's entire quarterback room.
Over the weekend, Allen's former team found that out the hard way. The Denver Broncos lost all three quarterbacks for Sunday's defeat to the New Orleans Saints because of contact tracing. Meanwhile on the same day, Allen ascended from an emergency role to be the Bengals' starter against the New York Giants, for a different reason. With starter Joe Burrow lost for the season with a knee injury, Allen got the starting nod over second-year QB Ryan Finley.
Allen serves as the prime example of what playoff teams will need to stay on track this season -- the COVID-19-proof quarterback.
For Allen and the Bengals (2-8-1), his isolation from the other two quarterbacks on the roster proved to be a prudent move.
"He always met virtually away from everybody else," Bengals coach Zac Taylor said after Sunday's 19-17 loss to the Giants. "And even on [the] field, I often lectured him about standing too close to the other players. He had his helmet on and could listen, but that's just a part of what we've got to do now."
A major hurdle for every NFL team is balancing safety with trying to be competitive and complete the season. If anyone is within six feet of a person who tests positive for COVID-19 for five or more minutes, they are deemed a close contact.
The 28-year-old Allen, who spent the 2019 season with the Broncos and made three starts, arrived in Cincinnati toward the end of training camp as a contingency plan.
During training camp, the quarterbacks met virtually in separate rooms. In the portions of practice open to the media, Allen was often seen throwing to wide receivers during individual drills while Finley and Burrow worked together during team drills.
Once Burrow went down for the season with a left knee injury on Nov. 22, Allen's role changed. He bumped Finley as the next-best option. On Nov. 25, Allen participated in team drills for the first time since he joined the Bengals.
"That first [Nov. 25] practice was good for the whole team to see the throws being made," Allen said. "I tried to talk to as many guys as I could and get to know a lot of the guys, but this season with COVID-19 is a very strange season."
Allen's first game since Week 12 of 2019 went about as expected. He was 17-of-29 passing for 136 yards with one touchdown, one interception and a lost fumble on the Bengals' final drive, which sealed their third straight loss.
However, the performance was good enough for Taylor to declare Allen the starter for Sunday's game against the Miami Dolphins. On Monday, Taylor cited other factors that hindered the offense against the Giants -- penalties, turnovers, dropped passes and coaching.
Cincinnati deserves some criticism for its roster management. But when it comes to accounting for COVID-19, the Bengals have been proactive.
In addition to Allen's isolation, the Bengals also signed kicker Austin Seibert after Week 1 and placed him on the active roster in case something happens to starter Randy Bullock. Vanderbilt ran into that dilemma on Saturday and made history when soccer player Sarah Fuller became the first woman to compete in a Power 5 football game.
"At the specialists' positions -- and I'm talking quarterbacks -- that's tough sledding if something goes wrong there," Taylor said.
Not every coach agrees with the philosophy, however, even after what happened to the Broncos. New England Patriots coach Bill Belichick said he has no intention of isolating third-string quarterback Jake Dolegala, who held the same role in Cincinnati last season.
"I don't think you can really practice and play very well doing it that way," Belichick told local reporters. "So at some point, you have to meet, prepare and play. I'm sure if we all stay around in a bubble, maybe nobody would get anything, but I can't imagine we'd be a very good football team."
Taylor said he didn't feel vindicated about how he handled Allen through the precarious season. With the Bengals down to two quarterbacks, Kevin Hogan will replace Allen on the practice squad as the emergency option.
In an ideal scenario, Hogan never comes close to taking a snap for Cincinnati this season. But if something happens to Allen or Finley, the Bengals are hedging that they'll have an available option.
"Nobody has the exact right answer in how to handle everything," Taylor said. "You just have to do your best to think you're doing what's right."
ESPN.com's Mike Reiss contributed to this report.