PITTSBURGH -- Los Angeles Chargers quarterback Philip Rivers has a chance to finish his career with at least 400 touchdowns and 55,000 passing yards. A fine quarterback, indeed.

But a recent tweet from Pro Football Focus about Rivers' place in the 2004 quarterback class prompts a few double takes.

Chargers QB Philip Rivers leads the QB class of 2004 in terms of average PFF grade from 2006-2016. pic.twitter.com/z6Hz9ARTys — Pro Football Focus (@PFF) May 16, 2017

In a "career QB comparison" from 2006 to 2016, PFF gives Rivers a 84.6 average overall grade, a tick higher than the Pittsburgh Steelers' Ben Roethlisberger (84.2) and well above the New York Giants' Eli Manning (75.0).

This can be viewed as an upset, considering Roethlisberger's 123-60 career record and two Super Bowl wins.

In PFF's system, players receive a grade from 0 to 100 based on an analysis of every down they play and their performance within that play. Each play ranks on a scale of minus-2 (awful across-body interception, for example) to plus-2 (a dime down the sideline tightly placed between corner and safety). Situational football is part of the equation, and several former NFL coaches are involved in the grading process.

Based on the grades-by-year chart, Rivers was ahead of Roethlisberger early in his career, and despite slipping behind in the previous three years, he still held the overall advantage.

Perhaps Rivers has the numbers to make things interesting. Roethlisberger has the slight edge in passing yards with 46,814 compared to Rivers' 45,833. Rivers holds the touchdown advantage, 314 to 301. Both are 64 percent passers. Roethlisberger (94.1 career passer rating) has 160 interceptions to 156 for Rivers (94.7 passer rating).

Roethlisberger has been dynamic in his mid-30s, averaging 302.5 passing yards per game to Rivers' 280.5. Rivers is 97-79 as a starter, far below Roethlisberger's record.

Based on the proverbial eye test, however, Big Ben is a big winner. An informal sampling of five evaluators -- coaches, scouts and a former NFL exec -- favors Roethlisberger 5 to 0. Former Browns general manager Phil Savage says he likes both but "Ben is special -- huge, tough, gamer, winner."

Roethlisberger's .672 winning percentage strengthens his place in the NFL's quarterback pantheon.

"For some reason, people are reluctant to put him in that group," ESPN analyst Louis Riddick told me in late 2015. "But teams are scared to death of him like they are Tom [Brady] and Aaron [Rodgers]. I would say there is no gap and you would put him right there."

All three quarterbacks from the 2004 draft might end up in the Pro Football Hall of Fame. And they have a few more years to punctuate their careers. But the PFF grade is at least a mild surprise to many who have followed them closely.