As is the case most years, the 2012 Chicago Marathon features so many participants, it's often difficult to distinguish one runner from rest of the 45,000-person pack.
Except, of course, when it comes down to the final mile or two before the finish line.
This year, there are a number of well-known marathoners running in Chicago, and each have decent odds at coming home with the 2012 title.
Here's a look at some of the brightest stars to watch at this year's edition of the Chicago Marathon.
As one of the most successful female marathoners in the world, Liliya Shobukhova is the heavy favorite, and to put it mildly, she has a record of success in Chicago.
In fact, Shobukhova is shooting to become the first woman ever to win the Chicago Marathon four times, and no one's beaten her in Chicago since 2009.
If anyone but Shobukhova wins on the women's side, consider it an upset of epic proportions, because the Russian star has only lost twice in major marathons since 2009.
After finishing the 2011 Chicago Marathon in second place to fellow Kenyan Moses Mopop, Wesley Korir is hungry to claim his first win in Chicago.
With Mopop out of the race due to injury, Korir's chances are significantly better in 2012, and seeing as the former University of Louisville product is fresh off his 2012 Boston Marathon title, he's got to be considered the favorite to win on the men's side.
Running a marathon is difficult enough, but running one blindfolded sounds downright crazy.
However, that's what 36-year-old EJ Scott is attempting to do at the 2012 Chicago Marathon, and for a very worthy cause. The Chicago Tribune recently chronicled Scott's quest:
Scott suffers from a rare retinal degenerative disease, choroidermia, which eventually leads to total blindness. And though he has been running regularly for the last few years, this year he set an ambitious goal: to run 12 marathons in 12 cities in one year while raising more than 100,000 dollars for research for choroidermia.
Scott won't win on Sunday, but it's impossible not to be rooting for him and his cause.