When comparing athletes through the prism of different eras, context is vital. As the game changes, we simply cannot make blanket statements regarding stats.
In Major League Baseball, the drastic changes the game underwent, from the Dead Ball Era to the Steroid Era, make comparing Hall of Fame players across decades a very difficult task.
When it comes to Halladay's Cooperstown credentials, context is everything. If the voters simply look at his body of work in relation to every pitcher across the decades of baseball history, expect him to fall short of induction time and again. In fact, Halladay's 3.38 career ERA doesn't rank in the top 300 in the history of baseball.
Some names ahead of him on that list of luminaries: Orvall Overall, Sam Leever and Hippo Vaughn.
If you remember watching those pitchers at the turn of the 20th century, congrats. For the rest of us, adjusted ERA, or ERA-plus, is a much, much better way to evaluate Halladay's place in the record books.
Without context, Halladay's 3.38 ERA is really good, but not legendary. When factoring in when and where he pitched, the equation changes.
From 1998-2009, Halladay pitched in Toronto's Sky Dome, later renamed Rogers Centre. Using ESPN's MLB Park Factors, we can see how difficult it was to pitch there during those years. In Halladay's 12 years in Toronto, his home park yielded home runs at a prolific rate, ranking in the top 10 in the league six times from 2001-2009.
Of course, those numbers, along with almost every offensive number in baseball, were shaped by the Steroid Era. Regardless of your definition of when the offensive explosion began in baseball, Halladay undoubtedly pitched in it. From 1998-2003, runs per game across the sport never dipped below 4.62, making double-digit-run games more commonplace than shutouts.
When factoring league and park effects into the equation, Halladay's adjusted ERA stands out among the pitching titans in the history of the sport.
Upon retirement, Halladay owned a career 131 ERA+. That figure is tied for 13th all-time among pitchers currently in the Hall of Fame or on the current ballot. Some names below Halladay on that list (subscription required): Bob Gibson, Jim Palmer, Tom Seaver and Steve Carlton.