Chicago Cubs: 5 Stars Who Need to Step Up ASAP Before It's Too Late

The Chicago Cubs are in first place in the National League Central entering play Friday.

Other than that, not much has gone according to plan for the MLB champions.

At 63-57, the Cubs have the worst record of any division leader in baseball. Their plus-49 run differential is the sixth-best mark in the National League, behind the Los Angeles Dodgers, Washington Nationals, Arizona Diamondbacks, Colorado Rockies and St. Louis Cardinals. 

A team that was supposed to dominate one season after burying the billy goat has barely managed to keep its horns above water, at the risk of mixing metaphors. 

Here, then, are five Cubs stars who need to step up in the season's final month-plus, before it's too late.

We're defining "star" as guys with either an extensive track record, loads of potential, a massive paycheck or all of the above. And we're paying extra attention to underperformers with the ability to nudge the Cubbies' foundering fortunes northward.

INF/OF Ben Zobrist

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Ben Zobrist is 36 years old. That's an age when plenty of players' skills erode for good.

So it's easy to look at his .223 average and .671 OPS and assume this is the end of the line for the veteran super-utility man and three-time All-Star.

To hear Zobrist tell it, however, he's got something left in the tank.

"Am I doing the things I need to do to have a good, quality at-bat? If I can start doing that again, then I'm very confident that when we get to that time, I'll be able to do what I normally do," he said, per CSN Chicago's Patrick Mooney. "But that's a long ways away for me, still."

With the playoffs fast approaching, that "long way" had better be relatively short.

LHP Jose Quintana

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Jose Quintana hasn't been awful since the Cubs acquired him from the cross-town Chicago White Sox at the trade deadline. 

He hasn't been great, either.

Remember, the Cubs gave up top position prospect Eloy Jimenez, top pitching prospect Dylan Cease and two other minor leaguers to acquire Quintana.

The southpaw wasn't merely a rental, as he's inked to an affordable deal through 2020 with a couple of team options. The Cubs, though, got him to help them in the here and now.

Quintana has lost three of his last four starts with the Cubs, surrendering 14 runs in 22 innings. He sports a 5.63 ERA in August, which compares unfavorably to his 4.33 ERA on the season.

"I'm just trying to do my job and hit my spots," Quintana said, per CSN Chicago's Tony Andracki. "But definitely not [putting too much pressure on myself]. Things are a little new for me here, but I feel pretty good, so no pressure on me."

That's a nice line, but with the Cubs' starting rotation sporting a 4.28 ERA despite a recent resurgence by right-hander Jake Arrieta, Quintana should feel his share of pressure.

LF Kyle Schwarber

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The Cubs have been waiting all season for Kyle Schwarber to find his groove, and maybe he finally has. 

The 24-year-old slugger has six hits in 10 at-bats in his last four games, including a home run. 

"I'm fine now," Schwarber said on Thursday, per Steve Greenberg of the Chicago Sun-Times. "I can't be worried about what the board says, and I'm not."

Sorry, Kyle, we'll worry about the board on your behalf. His recent hot streak aside, Schwarber is hitting a scant .204 while posting minus-four defensive runs saved, per FanGraphs. 

The fourth overall pick in 2014, Schwarber is bursting with potential, which he flashed in 2015 and during last year's inspiring postseason.

Now, he needs to sustain it for the 2017 stretch run.

SS Addison Russell

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After clubbing 21 home runs with 95 RBI and making the All-Star team in 2016, shortstop Addison Russell has plummeted to Earth this season.

He owns a .241/.305/.417 slash line in 97 games, has faced domestic violence charges and is on the disabled list with a lingering foot issue.

The Cubs have enough depth and versatility to muddle through without Russell, but the 23-year-old was supposed to make the leap to full-blown superstar; instead he has been an inconsistent enigma.

In that sense, he embodies these Cubbies (im)perfectly.

RF Jason Heyward

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Jason Heyward is the top defensive right fielder in the National League, according to FanGraphs' measure. He hasn't been a complete disaster at the plate, either.

You could argue he's doing his job.

Consider, though, that Heyward is making more than $28 million this season. If he doesn't opt out of his contract, he'll make another $20 million in 2018. If he doesn't opt out after that, he'll make $86 million through 2023.

Now, weigh Heyward's .697 OPS and eight home runs from a position that is traditionally supposed to generate power.

The Cubs didn't sign him to be a defensive specialist. With other key hitters struggling/inactive, they need him to earn his money at the plate as well as in the field. 

"I have a lot of faith in this fellow," manager Joe Maddon said of Heyward, per USA Today's Jorge L. Ortiz. "He's very strong mentally and physically, and I think he's going to be in good shape for the last part of the season."

The Cubs faithful can only hope.

All statistics current as of Thursday and courtesy of MLB.com and FanGraphs.