That means run as hard as you can to first base, and to second and wherever else dirt ends with a base. It's meant to ensure players play as hard as they can and that his club doesn't lose due to lack of effort.
For two consecutive games now, it's been this rule -- abided by a player long accused of not complying with such ideas -- that's led to Cubs victories. Never mind all the talk of magic.
"That's the only rule he has," said Starlin Castro, whose hustle led to the go-ahead run in Thursday's win. "Respect the 90. Run hard on every ball. And that's what everybody does."
Castro hasn't always found favor with his managers throughout his career for what at various times has appeared to be lackadaisical play. But his hustle truly made a difference this week against the Mets.
"Give him credit," Maddon said.
Thursday, Castro's effort running to first forced Mets third baseman Daniel Murphy to throw away Castro's slow roller in the fifth. Castro advanced to second and scored the go-ahead run one batter later.
Wednesday night, Castro legged out an RBI infield single to break a scoreless tie in the 11th. On both occasions, Castro put his head down and ran, forcing the opponent to make a mistake.
The Cubs won both games and all three against New York.
"Every [manager] has their different things. But everybody likes players when they hustle. We try to hustle every day -- that's how we play baseball," Castro said. "It's important, especially when you are struggling, to do whatever you can to get that hit."
Joe Trezza is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.