Halley's Comet appears visible to the Earth once every 75-76 years. Todd Haley's hiring as offensive coordinator is another strange occurrence for the Pittsburgh Steelers.
It has been a long time since the Steelers hired an outsider to run the offense. You have to go back to 1999 (Kevin Gilbride) to find the last offensive coordinator that was hired by the Pittsburgh Steelers from outside the organization's coaching staff. That's a long time in the NFL.
Haley served as the offensive coordinator for the Arizona Cardinals for the later part of the 2007 season and full time for their run to the Super Bowl in 2008. That season saw the Arizona Cardinals put up a franchise record 427 points and averaged 365.8 Yards per game, good for fourth in the NFL. They nearly pulled off a stunning upset in Super Bowl XLIII against the Steelers.