It might just be one of Colts.com's many season reviews, but '98 was especially significant in laying the groundwork for the last decade and a half of Indy's success. Far less depressing than its predecessor (1997's "turning point" was a Buffalo game in which the Colts blew a 26 point lead), 1998 saw the beginning of the "Peyton Manning" era, if not the beginning of the "Winning" era.
Colts.com writer Tom Rietmann has the season overview here. My favorite quote:
“It’s good to get a win and know that we are capable of doing it,” Manning said after gaining the victory over his fellow rookie quarterback, Leaf. “Hopefully, there will be a lot more to come.”
Besides the irony of Manning and the Colts taking off, Leaf fizzling out, and San Diego going on to ruin a perfect season bid and multiple playoff runs after his departure, it's nice to look back on moments like that. It's also fun to consider that, with a better running back by far (Marshall Faulk), and Marvin Harrison, Manning only managed three wins - eight less than Andrew Luck's Colts, less than 15 years later.