Peyton Manning Broncos 2015
Broncos quarterback Peyton Manning could trot out on an NFL field for the last time when Denver hosts New England for Sunday's AFC Championship. Getty Images

There were mile-high expectations for Peyton Manning when he entered in the NFL in 1998. The son of a two-time Pro Bowl quarterback, Manning endured a brutal rookie campaign, with just a 56.7 percent completion rate and an awful 28 interceptions as a member of the Indianapolis Colts.

But Manning persevered. He would wouldn’t miss a game with the Colts over 13 seasons and was selected to 11 Pro Bowls, winning his only Super Bowl title in 2007. After sitting out the entire 2011 season, there was no rocky transition for Manning as he left the Colts to join the Denver Broncos. Manning consistently put the Broncos in Super Bowl contention, and has Denver hosting the New England Patriots on Sunday with a Super Bowl berth in the balance.

This epic battle between Manning and Patriots quarterback Tom Brady may not just be the last time we see the two duel against each other, but it might be the last time Manning plays an NFL game. Despite a season in which Manning is back the AFC Championship yet again, this has arguably been his worst season since his rookie season. At age 39, the injuries appear to have taken their toll on Manning to the point that he has to consider retirement.

Are we seeing the last of Manning, one of the greatest quarterbacks of all-time? Could Sunday be his very last game?

Considering Manning's 2015 stats, and the fact the Patriots are favored, it sure does look like it. Quarterbacks of Manning’s stature understandably have a great deal of pride, and it would likely be difficult for him to finish his career like Brett Favre, sticking around too long and looking like a shadow of his former self while consistently being out of title contention.

But that’s the doomsday scenario. Manning also has the chance to go out like a hero. He can outshine Brady, and reach the Super Bowl. Then he could go out as a Super Bowl winner. Why not, right? Stranger things have happened.

Still it’s a bit unsettling how Manning has dipped this season, and how this seems to look like his final season. Retirement talk was inevitable even before some poor performances this season, given Manning's age and injury history. Yet, Manning might stick it out in 2017, no matter what happens on Sunday or in the Super Bowl.

In November, NBC Sports' Mike Florio cited a source who claimed Manning not only intends to overcome a season of injuries but will play beyond the 2016 season. In September, Manning was asked by Yahoo Sports about any thoughts on retirement, and he quickly demurred under the weight of the impending season.

"I guess with 12 days or 11 days before the season starts, I don't have those thoughts," Manning said politely. "I think about playing football to the best of my ability in 2015. I understand it's a fair question when you have the opportunity to ask it. But with a little over a week before the season starts, I'm kind of fired up to be playing and looking forward to making 2015 a special year."

There is no denying that Manning endured a difficult season, and there are some doubts he can compete at a high level. While he put together a respectable showing against the Pittsburgh Steelers on Sunday, despite numerous dropped passes by his receivers, Manning may not want his legacy tainted by more setbacks.

In the AFC Championship, the attention is back on Manning and his “rival” Brady, with the Broncos and Patriots still the elite teams in the AFC. Winning one more game against the Patriots star would be a satisfying feeling for Manning.

In their previous 16 career games, Manning is 5-11 against Brady, including 1-3 in the last four meetings with Manning’s sole win in that span coming in 2013’s AFC Championship.

Their postseason records do, however, give Manning a shot to move on to his third Super Bowl. In four career postseason showdowns, Manning’s gone 2-2 against Brady, owning a 2-1 mark in championship games and 2-0 at home. And home field’s played a major role in the rivalry as well, as neither Brady nor Manning’s pulled off a road victory against each other since 2007.

But in all those previous matchups, Manning was a far different quarterback. The record-setting and breaking five-time MVP is still one of the smartest field generals in the game, but his body can no longer keep up with his great football mind.

Beginning last season, when Manning was dealing with a torn thigh muscle, the decline was already evident. Over Denver’s final four regular season games of the 2014 season, Manning’s arm strength waned and with it his dominance in the pocket. He heaved three touchdowns to six interceptions and largely relied on the Broncos stacked defense to close out the season before falling to Andrew Luck and his old Colts in the AFC Divisional Round, completing 26 of his 46 passes for 211 yards and one score.

Amidst predictions and prognostications from media members, this year the drop-off was far more obvious and many believe Manning will finally step away. Again, injuries slowed his production and eventually cost Manning his starting job for the first time since he was a freshman at Tennessee. A torn plantar fascia in his left foot and a rib injury sidelined Manning for six games this year, forcing Denver to turn to Brock Osweiler, who went 5-2 in seven starts.

Yet even before the injuries set in, statistics were quick to point out Manning’s steep decline. He was leading the NFL with 17 interceptions, something he hadn’t done since his first year in the league. Manning was also on pace for his worst completion percentage that rookie season, 59.8, and his 224.9 passing yards per game were by far the lowest of his career.

And even though he managed to beat the Steelers, vintage Manning was not on display. For just the second time in his career, and over 25 postseason starts, Manning failed to throw a touchdown and his team won anyway. He went a decent 21-for-37 for 222 yards and a 74.4 passer rating against a punishing Steelers defense that constantly pressured him in the pocket, taking a respectable 1.0 sack and three more hits.

Still, next up is a Patriots defensive frontline that sat behind only Denver for the most sacks during the regular season, making a repeat of Manning’s performance against Pittsburgh a likelihood and almost a certainty.

And what figures to be his final performance should be reason enough to walk away with one year remaining on his current contract. Manning is owed $19 million in salary for the 2016 season, and another $2.5 million in bonuses.

At this stage of his career, walking away with dignity probably has far more value to Manning.