He was about to get his first meaningful NFL snaps, and life for them both was about to take a dramatic turn.
"I probably hyperventilated for a couple of minutes and then realized, 'You know what? He's been in really high-pressure situations before. He's good,'" Katherine McCarron (formerly Katherine Webb), the ex-Miss Alabama and model who married the quarterback more than a year ago, told ESPN this week.
"This is where he thrives," she said. "So I had to ease it down for myself."
From the moment starter Andy Dalton broke his right thumb in Sunday afternoon's loss to the Steelers, forcing McCarron to replace him for the foreseeable future, very little has slowed for the young couple. Things got so hectic once they got home after the game that the McCarrons turned off their phones, and opted instead to watch a movie and some "SportsCenter" before bed.
Hit that day with an emotional roller coaster of pain, joy, heartache, excitement, nervousness, pride and disappointment, the McCarrons still find themselves trying to wrap their minds around what the next week, three weeks or month could look like for their family.
Last Tuesday, they announced they were expecting a baby boy. This Tuesday, AJ is digesting much more about this Sunday's opponent, the San Francisco 49ers, than he previously imagined he would have to. If the Bengals (10-3) are going to return to Levi's Stadium for the Super Bowl in February, they will need a well-prepared McCarron to help lead them there.
"He could take us to the Super Bowl," Katherine said. "I thought about that [Sunday] for the first time and it just kind of gave me chills. And at the same time, I have Andy in the back of my mind. Andy has taken us through the whole season and in my mind, I'm like, 'I would love for AJ just to be able to do it for him and for the team.'"
There is a chance Dalton returns before the playoffs with the news Monday that his thumb won't require surgery.
Part of the McCarrons' desire for isolation at home following Sunday's game stemmed from the two interceptions AJ threw. Sure, he came in off the bench cold to throw for 280 yards and two touchdown passes in three quarters, but his head space was more preoccupied with the picks.
"Here, in this household, we haven't really dealt with a lot of losses. And we haven't really dealt with a lot of interceptions, either," Katherine said. "He's definitely a perfectionist when it comes to his craft. So he wants everything to be on point, and he knows exactly what he has to do and whenever he makes a mistake, it's horrible. He takes it so bad. That's just the way he is. He's just super competitive. So you have to let him know: 'It's OK. People make mistakes.'"
Short-term memory can be an NFL quarterback's best friend.
While at Alabama, AJ went 36-4, was part of two national championship teams, was a Heisman Trophy finalist, and had an NCAA record-low 1.46 interception percentage. That resume has Katherine convinced her husband is the man the Bengals need right now.
"He probably feels like he has the weight of the world on his shoulders to carry the team the rest of the way through the season, and even into the playoffs," Katherine said. "But just what I've seen him go through in college and his confidence back then and how he responded then, I have no doubt in my mind that he will be able to do the same thing here."