From a purist’s perspective, Denver Broncos quarterback Peyton Manning’s record-setting 510 touchdown passes are skewed by the fact that he played his entire career in an era of unprecedented success for passing offenses throughout the NFL. However, the 38-year-old Manning’s on-field accomplishments are considered transcendent by nearly any measure, including the traditional statistics by which past players were ranked, or the advanced metrics favored by today’s statisticians.

“I think when you look at that total career touchdown pass number, it’s skewed toward newer folks,” said sports statistician Andy Andres, a senior lecturer of natural sciences and mathematics at Boston University. “It’s really a big difference when you just count the number of touchdowns because [today’s NFL] is definitely more of a passing game. Current quarterbacks are going to get a lot more touchdowns when you just add everything up.”

It’s difficult to compare a modern NFL quarterback’s statistics to those of former Chicago Bears star Sid Luckman, Cleveland Browns great Otto Graham or other legendary quarterbacks from past eras, as the NFL’s ever-changing rules force constant alterations to play style and effectiveness. Manning plays in an era where rules designed to protect the passer and prevent pass interference from defensive backs have allowed quarterbacks to throw for more yards and touchdowns than ever before in NFL history. For example, the league's single-season touchdown record changed hands just once from 1962 to 2003, but was broken three times from 2004 to the present – most recently by Manning’s 55 touchdowns in 2013.

For a more accurate measurement of quarterback’s on-field performance in the modern game, Andres prefers a stat called defense-adjusted yards above replacement, or DYAR. Pioneered by statistician Aaron Schatz of FootballOutsiders.com, DYAR measures a quarterback’s total value through a formula that calculates how many more yards a given quarterback produces compared to an average, replacement-level quarterback, adjusted for situation and opponent. It’s similar to baseball’s wins above replacement, or WAR, which measures how many wins a given player adds to a team’s record compared to an average replacement.

In terms of DYAR, Manning is one of the dominant players of his generation. Since his first season in 1998, Manning has finished in the top five of the league in this category 13 times. Moreover, he has produced two of the league’s top three DYARs since 1989, his 2,475 DYAR in 2013 second only to New England Patriots quarterback Tom Brady’s 2,674 DYAR in 2007.

“Peyton is like [MLB legend] Ted Williams,” Andres said. “He’s the best. But Tom Brady is Joe DiMaggio. They’re considered rivals and equals, but when you really look at it, Peyton’s had the better quarterbacking career.”

Another valuable measure of quarterback performance is Total Quarterback Rating, an ESPN-developed advanced metric that uses various statistics to rank each player on a 0-to-100 scale. Again, Manning’s numbers are astronomical. Since the stat was devised in 2006, Manning has recorded six of the NFL’s 10 best single-season QBRs, including an all-time best mark of 87.22 in 2006, according to Pro Football Reference.

A closer look at more traditional touchdown-based statistics provides additional context to Manning’s prolific on-field performance. Throughout his career, 5.9 percent of Manning’s pass attempts have ended in a touchdown – a rate second only among active players to Green Bay Packers quarterback Aaron Rodgers’ 6.5 percent. Manning recorded his best single-season mark in 2004, when his then-record 49 touchdown passes yielded a 9.9 percent touchdown rate, sixth-best in NFL history.

Manning’s statistical dominance is a testament to his unwaveringly strong play. In 246 career games over 16 NFL seasons, he has averaged 2.07 touchdown passes per game. In all, Manning required about 1,500 fewer pass attempts than future Hall of Famer Brett Favre, the NFL’s previous record-holder for career touchdown passes.