CHICAGO -- It's been a very creative summer for the Cubs. As the magic number for the Cubs to clinch the National League Central title for the first time since 2008 reaches the teens, the only debates now are who came up with the best T-shirt design and who will win the NL Most Valuable Player Award.

Manager Joe Maddon started the T-shirt craze in an effort to raise money for his Hazleton Integration Project, but some of the players have created their own, including Jon Lester 's "Bunt to Win" and another from David Ross promoting Anthony Rizzo for the 2020 Tokyo Olympics because of his acrobatic catches.

The MVP discussion focuses on Rizzo and Kris Bryant , who was the starting third baseman for the NL All-Star team, but also has played well in the outfield. Rizzo has a slight edge in RBIs over Bryant, while Bryant has hit more home runs. Whom do you pick? It depends on who delivers the game-winning hit that day.

But they're not the only ones. The Cubs also have gotten plenty of offense from 22-year-old shortstop Addison Russell , who has set career highs in home runs and RBIs in his second season. He's done so well, Maddon has moved him up in the lineup, ahead of Jason Heyward , who has played Gold Glove right field but has scuffled at the plate.

They've all contributed to the Cubs' obscene run differential, which was more than 200 heading into September. Last season, Heyward watched the Cubs win 97 games to secure an NL Wild Card spot. He opted to leave St. Louis and sign with Chicago in the offseason.

"We're a good team," Heyward said of the Cubs. "I said it in the offseason and earlier this year, when you have a team with this majority of young guys and they go into the playoffs and get experience -- any experience is good experience. They've shown to themselves and shown to everybody what they can do. I'm not surprised, by any means. It's fun for me to add to it and feed off them and let them feed off me."

But the real reason the Cubs have run away with the NL Central is their pitching. All five starters -- Jake Arrieta , Lester, John Lackey , Jason Hammel and Kyle Hendricks -- have been in the top 20 in ERA for most of the season. Hendricks heads into September leading the Major Leagues with a 2.09 ERA. The right-hander went 4-0 with a 1.28 ERA in August. Remember, he's the fifth starter.

The bullpen got a boost with the addition of flamethrower Aroldis Chapman , and once Héctor Rondón and Pedro Strop return from the disabled list, the relief corps will be even more potent.

Maddon has emphasized he's only thinking about today, and the players are trying not to look ahead.

"It's definitely one game at a time, but it's starting to enter our minds of how many games do we have to win to clinch," Rizzo said. "We have to stay focused and keep playing."

The Cubs' toughest test in September may be their first series of the month, when they host the Giants in a four-game series that starts Thursday. There are also six games remaining against the Cardinals (Sept. 12-14 at Busch Stadium; Sept. 23-25 at Wrigley Field), and one more Interleague series Sept. 9-11 in Houston.

Besides keeping everyone healthy, Maddon's only concern is making sure the players get enough rest in the final month. Batting practice is optional most days. They may use a six-man rotation.

Keep an eye out for more slogans, especially those linked to Ross. The 39-year-old catcher is retiring at the end of the season. The hottest T-shirt in the clubhouse? Those touting Grandpa Rossy.

The road ahead

The Cubs have been able to take advantage of their large lead in the NL Central by putting Rondon and Lackey on the DL. Both are expected back early September. Rondon and Strop will be key setup pitchers for Chapman. What's helped propel them lately is the continued development of rookie catcher Willson Contreras and right-handed reliever Edwards, and contributions from lefty reliever Rob Zastryzny .

• Home games: 14

• Road games: 16

• Games vs. teams over .500: 17

• Two key series: Sept. 1-4, vs. Giants; road/home vs. Cardinals, Sept. 12-14 at Busch Stadium and Sept. 23-25, at Wrigley Field

• Help on the way? More important than any callups are the players coming off the DL. The list includes: Lackey (right shoulder strain) expected back early September; Rondon (right tricep strain) expected back early September; Strop (torn meniscus left knee) expected back mid September; RHP Joe Smith (left hamstring strain) expected back early-to-mid-September.

• Callups: IF Tommy La Stella was batting .295 before he was optioned to open a roster spot. He's a good lefty bat off the bench and provides middle-infield help. Other possible adds include Almora and IF Jeimer Candelario

• Cause for concern? Maddon wants to make sure the starting pitchers conserve their arms for the postseason. He believes in rest -- he thinks batting practice is overrated. The Cubs may go to a six-man rotation to do that, and use lefty Mike Montgomery . The players promoted will be "pertinent," Maddon said, and be used to give regulars a breather late in games.

Carrie Muskat has covered the Cubs since 1987, and for MLB.com since 2001. She writes a blog, Muskat Ramblings. You can follow her on Twitter @CarrieMuskat and listen to her podcast.