CHICAGO, IL - MAY 05: on May 5, 2014 at Wrigley Field in Chicago, Illinois. (Photo by David Banks/Getty Images) *** Local Caption *** The Cubs' Nate Schierholtz slides safely into second in front of the White Sox's Gordon Beckham. (David Banks/Getty Images)

(CBS) As the White Sox scored twice in the 12th inning to pull out a 3-1 win against the Cubs at Wrigley Field last night, a question lingered.

Why was the city’s big Crosstown Classic series being contested in early May, on a weeknight, amid the hoopla of the Blackhawks’ playoff run, on NFL Draft week and in front of a sparse crowd thinned out by chilly weather in the 40s?

MLB senior vice president of scheduling and club relations Kate Feeney joined the Mully and Hanley Show on Tuesday morning to explain.

“We went to 15-15 — there are now 15 teams in each league,” Feeney said. “So there has to be an interleague series in every slot, if you look at the schedule. We have 30 teams, not just two.

“There has to be interleague games every day, basically, other than off days. They’re spread out throughout the season. We no longer have a (block) of interleague. Next year, when teams are playing corresponding divisions — when East is playing East, Central-Central, West-West — they will go back to three and three (games at home and away). But right now, the number of series we have to play to get the 162 games in 183 days, we have to have one what we call ‘squeeze week,’ which is the three series within one week. And for travel purposes and other reasons, the natural rivalries — because obviously they’re teams that are very close to each other — for travel reasons, we put back to back.

“It could change after a few years. And as I said, next year it will go back to three-three.

“To get the agreement with the union, they wanted teams playing as close as possible the same number of games versus the same teams within the division. And the prime rivals are sort of pulled out from that.”

“If you look at all the other natural rivals, they’re all twos-twos.”

Listen to the full interview below.