The Chicago Cubs set out to defend their long-awaited World Series title in 2017 but have instead spent the season dancing with the .500 mark and lagging behind in the NL Central race.

Not to worry, though. These are things they can and will fix.

Provided he or she is foolhardy enough, an optimist could probably come up with dozens of reasons to believe the Cubs will shake off their disappointing season to retake the NL Central. Here, a simple five will do.

Let's get to it.

Note: All stats within are current through Tuesday, July 4.

Their Best Lineup Synergy Is Ahead of Them

The Cubs' lineup could do it all in 2016, ranking third in runs per game and first in defensive efficiency. This year, it's fallen to 19th and fifth in those two categories, respectively.

Yet things are looking up.

Chicago's offense has been better lately. The team managed just a .727 OPS through its first 63 games. It's managed a .789 OPS in 20 games since. Anthony Rizzo, Kris Bryant and Willson Contreras have led the way, with a little help from new friend Ian Happ.

More recently, the Cubs welcomed Ben Zobrist and Jason Heyward back after both spent several weeks on the disabled list. It can only help to have Zobrist's many talents back. And even if his bat continues to be nothing special, Heyward is worth playing for his glove.

The next thing the Cubs have to do is get Kyle Schwarber back into the mix.

Knowing that his cold bat got him sent down to the minors in the first place, that may not sound like an exciting proposition. But if his 1.16O OPS in his 10 games with Triple-A Iowa is any indication, his stint in the minors could prove to be what he needed to get back on track.

Once everything comes together, the Cubs lineup of today should look more like the Cubs lineup of last year. All they'll need then is some pitching. And on that front...

Jake Arrieta Is Showing Signs of Life

Jake Arrieta's minor regression from 2015 to 2016 gave way to a major regression early this season. He began the year with a 5.44 ERA through eight starts.

Since then, the biggest impact he's had on the headlines is being the butt of snide comments from now-former Cubs catcher Miguel Montero. Lost in that drama, though, is that Arrieta has been better of late.

Go back to May 21, and he has a 3.35 ERA over his last nine starts. The OPS against him has dropped from .839 to .631, and his peripherals are looking good—all thanks to one pitch, apparently.

“My progress with the changeup is coming along real nice,” he said, per Steve Greenberg of the Chicago Sun-Times. “I’m getting more comfortable with it. It’s just allowing me to open up some more doors and be able to do some different things to right-handers as well as lefties. It’s a big pitch for me.”

After cratering in May, his changeup usage has been back up in the last two months. And he's used it to hold hitters to a .150 average during his hot streak. It could also be keeping hitters off his other offerings.

Nobody should mistake Arrieta for the untouchable, Cy Young-winning ace he was in 2015. But given the struggles of the Cubs' starting rotation, it's good enough that he's becoming reliable again.

There's another guy who can help in that regard...

Kyle Hendricks to the Rescue

Arrieta is the Cubs' resident Cy Young winner, and Kyle Hendricks is their resident ERA champion. Getting him back would be yet another big plus.

He has to get healthy first, as he's been on the disabled list since early June with a hand injury. There's now some light at the end of that tunnel. Carrie Muskat of MLB.com reported that Hendricks threw a bullpen session on Tuesday and showed no ill effects. He'll be back after the All-Star break.

Once back, Hendricks will need to get on a better track than the one he was on before his injury. He was following up his MLB-best 2.13 ERA from 2016 with a 4.09 ERA through 11 starts.

But it might not be that difficult for Hendricks to get squared away. 

His results look bad as a whole, but embedded within is a six-start stretch from late April to late May in which he had a 1.96 ERA while holding hitters to a .587 OPS. 

If Hendricks can produce more than just a flash of his old self when he returns, the Cubs will once again have an enviable trio of him, Arrieta and Jon Lester. That would provide an element of consistency that's heretofore been a missing ingredient for Chicago's rotation.

And if they need to make a move, so be it.

The Trade Deadline Is at Their Disposal

The Cubs probably have enough weapons already in house to seize the NL Central without any outside help. But why bother leaving that to chance?

From the volume of the buzz, the Cubs aren't going to. 

The July 31 trade deadline is just a few weeks away, and the Cubs are already popping up in rumors connecting them to big names. Jon Morosi of MLB.com reported that they've checked in on Detroit Tigers stars Justin Verlander and Alex Avila. Susan Slusser of the San Francisco Chronicle reported they've also scouted Oakland A's right-hander Sonny Gray.

It's all just noise for now, but the shoe fits.

President of baseball operations Theo Epstein is no stranger to big deadline deals, and he's well-positioned to make one or two more this summer. The Cubs are obviously in the hunt. And despite frequent promotions over the last several years, the team still has young talent to deal.

Following the 2017 draft, B/R's Joel Reuter ranked Chicago's farm system at No. 15 in MLB. That's not counting young major leaguers who could be expendable, such as Schwarber and Javier Baez.

As disappointing as Chicago's 2017 season has been, the takeaway should be that they have untapped upside and the potential to upgrade. It's hard to say the same about the team they're chasing...

The Milwaukee Brewers Aren't Running Away from Them

The Milwaukee Brewers have been surprising, but they're a rare first-place team that can't be called great.

At 46-40, their record isn't great. And despite how much the Cubs and the other three teams in the NL Central have struggled, the Brewers have yet to stretch their lead beyond 3.5 games despite holding first place for roughly half the season.

The reasons for this are mainly on the mound. Milwaukee's starting pitching is a mixed bag, and its bullpen has been a liability. These things make consistency hard to come by.

And better days aren't necessarily ahead.

They have to wait on Chase Anderson, one of their two good starters, to return from an oblique injury that could sideline him up to six weeks. And as the Cubs gear up for action at the deadline, Brewers owner Mark Attanasio indicated he's in no hurry to deviate from what was supposed to be a prolonged rebuild.

“If [general manager David Stearns] wants to come to me and say, ‘I want to blow up the big plan,’ his batting average is so high now, we’re going to listen to anything he recommends," Attanasio told Tom Haudricourt of the Milwaukee Journal Sentinel. "But, just from ownership to him, there has been no pressure to divert from the plan.”

The Brewers can't run away with the NL Central, nor do they want to. All the Cubs have to do is go get 'em.

Data courtesy of Baseball Reference, FanGraphs and Brooks Baseball.