Cubs loaded again — so what could go wrong as they defend World Series title?

MESA, Ariz. — There’s little reason to question the Chicago Cubs’ chances of returning to the World Series.

Their infield is loaded with young stars who haven’t even hit their prime yet. Their rotation contains two of the top three finishers in last year’s Cy Young Award race. Their bullpen features not one but two experienced closers. And their offense is getting back one of its most dynamic hitters in Kyle Schwarber.

Then again, the sight of the bulky brace supporting Schwarber’s left knee provides a reminder that things don’t always go as planned in baseball.

The Cubs’ ability to overcome Schwarber's injury-induced absence last season serves as testament to their deep reservoir of talent and grit. Despite having him for just two regular-season games and five in the postseason, they led the majors with 103 victories and shed the tag of lovable losers by claiming their first World Series crown since 1908.

A repeat is certainly within their grasp, even with the departure of valuable contributors like Dexter Fowler, Aroldis Chapman, Jason Hammel and David Ross. They have been replaced by Jon Jay, who will share center field with rookie Albert Almora, new closer Wade Davis and lefty Brett Anderson.

But before they can plan their next celebrations on Clark Street, the Cubs will need to address a number of issues that have the potential to derail their season, and they go beyond the unpredictable injuries – such as Schwarber’s last year – that inevitably crop up to a larger or smaller degree.

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Manager Joe Maddon has warned against complacency by saying he wants players to be “uncomfortable,’’ fighting the natural tendency to rest on their laurels, an especially big challenge for a group that has been lauded so much.

Among the questions to address that could become pitfalls:

How will Schwarber’s return play out?

Maddon plans to use him mostly in left field and as a leadoff hitter to take advantage of his on-base skills. Both of those raise red flags because the converted catcher, besides coming off the knee injury, looked out of place in the outfield at times during his rookie season of 2015.

“He runs better than you think, even with that brace on,’’ Maddon said. “He knows good routes, he throws well. I think he’s going to surprise a lot of people who have been down on him. I think he’s going to be a really good outfielder.’’

Schwarber said he spent much of the winter at the club’s spring training facility, working on his outfield skills and strengthening the knee. Midway through the offseason, he felt he could move in every direction with no restrictions. Schwarber is even catching some bullpen sessions in camp and is expected to be the club’s third catcher.

As for leading off, it’s nothing new to him. Schwarber said he did it 20-30 times while in college at Indiana.

“I’m not going to change the way I approach my at-bat,’’ he said, “but obviously, being the leadoff guy you want to get on base for the big dogs behind you.’’

Who’s on second?

Javier Baez’s emergence as a potential star with game-changing fielding ability bumped Ben Zobrist from second base to left field, and it was in that capacity that Zobrist won World Series MVP honors.

But left field is the only spot available for Schwarber, so Maddon will have to balance between the benefits of playing Zobrist – who had a healthy .831 on-base-plus-slugging percentage last season – and the need to get Baez on the field. He played all four infield positions with distinction in 2016.

“In a perfect world, everybody (healthy), it’s going to be tough to get him in there often enough at the beginning of the game,’’ Maddon said of Baez, 24. “But he’ll be fine. He’ll get his at-bats, the development will continue. He gets it. The game’s crazy. He's going to get plenty of at-bats before the season’s over.’’

Zobrist, who turns 36 in May, has made a career of moving from one position to the other and expects to do the same this year.

“That’s the player I am,’’ he said.

Can Jason Heyward rediscover his swing?

Though he remained an elite defensive right fielder, Heyward endured the worst offensive season of his career after signing an eight-year, $184 million contract with Chicago, batting .230 with seven homers and a .631 OPS.

Heyward spent the winter in Mesa reworking his mechanics to get closer to the hitting style he used in his earlier years, when he surpassed the .800-OPS mark twice in three seasons. Heyward’s current stance, with his hands lower and farther from his body, looks a bit like the one used by Anthony Rizzo.

Heyward has been pleased with how comfortable the changes feel, but the results will dictate how much difference they’re making.

“It’s something I’ve done before,’’ said Heyward, who is hitless in his first five Cactus League at-bats. “As baseball players and athletes, you go off muscle memory, and you also go off feel. … The biggest thing is to be relaxed, being tension-free, consistently being in a good position to hit.’’

How will they replace Ross’ presence?

Besides his role as Jon Lester’s personal catcher, the now-retired veteran was known as a clubhouse sage who helped keep the group striving toward the same goal.

Some people believe such contributions are overrated, that on-field performance is all that counts.

Zobrist is not among them, and he doesn’t think any one player can replicate what Ross did behind the scenes.

“You can’t fill that role. David Ross is one of a kind,’’ Zobrist said. “Every year is a new team. Collectively, the team has to find its personality. Rossy makes everyone around him better, by his attitude, by his energy. That’s what we’re going to miss, a lot. Hopefully, everybody else will do a better job of picking that up.’’

Veteran catcher Miguel Montero, who will back up Willson Contreras, could emerge as an influential figure in the Ross mold, although he believes those duties are better spread among several players.

Montero has cleared up some differences he had with Maddon – he had publicly criticized the manager after the World Series – and is not too concerned about complacency when he looks around the clubhouse.

He thinks back to how the city of Chicago reacted to the Cubs’ magical run and naturally wants to recapture that feeling.

“Once you experience winning the World Series and the satisfaction that comes with it, it motivates you to do it again,’’ Montero said. “It’s an unforgettable experience.’’

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