Aaron Rodgers and the Packers' victory over Dallas was the most watched NFL playoff game and biggest telecast in the country in more than a year. Reuters

Before the playoffs began, and really before Sunday’s two epic Divisional Round games, the NFL was experiencing a major television ratings drop. But fans showed that if the matchup is strong and the game is close towards the end, they will watch. That could open the door for another ratings bonanza for Super Bowl LI -- which would keep ad rates high.

Football and TV execs were watching closely Sunday, and with four of the league’s premier franchises, located in equally top markets, appearing in postseason games, the NFL set new ratings records. The Green Bay Packers' stunning last-minute victory over the Dallas Cowboys drew an average of 48.5 million viewers for FOX and peaked at 62.4 million when the game reached the final two minutes around 7:45 p.m. EDT, according to The Hollywood Reporter.

Other than the Super Bowl, the Packers-Cowboys became the most-watched telecast in more than a year and the most-watched NFL playoff game.

When primetime came, the Pittsburgh Steelers and Kansas City Chiefs also didn’t disappoint. NBC announced Monday Pittsburgh’s 18-16 road victory ended up being the highest-rated primetime game in league history for the Wild Card and Divisional rounds.

All told, NBC averaged 37.1 million viewers and peaked at 39.1 million.

Each game was the closest of these playoffs, which have been marred by one-sided victories with few thrills; that helps the NFL’s potential to make up for its ratings drop during the regular season.

Overall, the NFL experienced an 8 percent decline in ratings compared to last season and on average 1.4 million fewer people tuned in during the regular season, ESPN reported earlier this month. Primetime, with top networks like NBC and ESPN shelling out billions for rights, saw the biggest decline. ESPN dropped by 12 percent and NBC 10, while FOX and CBS saw their daytime game ratings slip 6 percent and 7 percent, respectively.

But Sunday’s ratings, coupled with the remaining teams vying for the two spots in the Super Bowl LI – to be played in Houston on Feb. 5 – could help the NFL bounce back. Along with Green Bay and Pittsburgh, the nationally popular New England Patriots and the Atlanta Falcons, who play in the eighth-largest TV market in the country – have the potential to boost the NFL’s sluggish ratings.

As Sports Illustrated reported after Super Bowl 50 last year, the last seven championship games rank as the seventh-highest rated television shows in U.S. history, and usually the closer the game, the bigger the ratings. For instance, the Denver Broncos blowout win over the Carolina Panthers drew 111.9 million to rank third all-time, but the top spot belongs to Super Bowl 49 between New England and the Seattle Seahawks, which came down to the closing seconds and hit a huge 114.4 million in ratings.

For the NFL and the networks that rotate Super Bowl broadcasting duties, drawing viewers is key to keeping the price for a 30-second commercial in the millions. Last, year a 30-second spot in Super Bowl 50 cost $5 million, and some analysts have questioned whether it’s a good move to put such a hefty budget into one ad -- a worry that the NFL can assuage if it keeps viewers glued to screens.

"I've always questioned how valuable it is compared to what you can do with that other $5 million on other kinds of television programs," Jim Nail, principal analyst for research and advisory firm Forrester, told CNBC last year.

But Nail also admitted that the commercials have their own role the day of the big game.

"The ads have become as integral to the program as the game. People are actually paying attention. You have to weigh that."