Much like Manning, Joe Montana was 35 when he suffered a serious injury.

With Peyton Manning officially joining the Broncos during a press conference this afternoon, today is a historic day for the NFL.

I don’t feel like I’m being overly dramatic with that statement, although the quest to make you click and read the words and letters I put together has made me stoop to far lower lows.

We may never see a quarterback of Manning’s caliber on the free agent market again. But when we witness history, a strange phenomenon occurs in which we lose sight of the present.

Amid the euphoria around the Interwebs and elsewhere yesterday two simple, common-knowledge facts were overlooked as we attempted to project Manning’s production in Denver, and how far he can take a team that was pushed by the hand of a superior overlord last year, and a unique offense.

Manning is old, and he’s still recovering from four neck surgeries. We all know this, mostly because it’s been written or said in every article, blog post, newscast, or Morse code communication that’s contained Manning’s name for at least the past year. Yet still as we discuss his future in the days and weeks ahead, the new car smell of Manning with the Broncos is intoxicating.

Reality sucks, and it’s a fun vacuum that kills all of our hopes and dreams. We’re not saying that Manning can’t be effective, or making any definitive statements about his ability to return to his elite form. But a little bit of perspective is key here as we move on from the excitement of Manning signing, to mini-camp workouts, training camp, and finally the 2012 season.

To gauge Manning’s potential numbers, theScore.com’s intern Devang Desai sifted through the digitally dusty stats at Pro Football Reference and looked back on the production of quarterbacks similar to Manning in physical stature during their age 35 and 36 seasons.

We start with the 35 year olds. The two exceptions are Joe Montana and Johnny Unitas, whose age 34 seasons were used because, like Manning, they sat out all or most of their age 35 season with injuries.

Production at age 35

Fouts threw the second most interceptions of his career at the age of 35. And prior to his 1996 season shown here, Marino only had one year with less than 20 touchdowns, and that came in 1993 when he played in only five games.

Production at age 36

Unitas is the most compelling comparison since he missed nearly all of the 1968 season, playing in just five games. The 1969 stat line shown here reflects a recovering Unitas after he tore tendons in his arm.

Prior his age 36 season, Unitas only had two years in which he threw more interceptions than touchdowns. His 12 TDs were his lowest total in a season when he started at least 10 games, and his -8 touchdown/interception ratio tied his career-low in 1961.