As part of MLB.com's Opening Day coverage, we are examining various aspects of each team. Today: The Great Unknown.

MESA, Ariz. -- The sound of the baseball hitting the catcher's mitt was loud, the kind of pop that did not require a radar reading to know that the fastball, unleashed by Yu Darvish, was at high velocity. Kyle Schwarber watched the pitch go by without a fight.

"Really?" remarked one teammate from behind the batting cage. "Right out of the chute."

It was clear from that first live batting practice session on Feb. 19 that Darvish's right elbow -- which required a scope in September after an injury-riddled season -- was fully recovered and fully operational. From his first mound workouts, the optimism surrounding Darvish has been overflowing. The only wrinkle has been a minor blister issue late in camp.

Darvish is expected to be ready for the Opening Day rotation, but where things go from there is the $126 million dollar question. That was the price the Cubs paid (over six years) to obtain the right-hander's services last offseason, only to have triceps and elbow troubles limit him to eight uninspiring starts in 2018.

The good news is that the Darvish who arrived to Mesa, Ariz., this spring has looked, acted and sounded like an entirely different person. The Japanese star has answered questions in English, without a translator nearby. He said that he feels the best he has in his entire career, and that he is smiling more than he ever has since coming to the big leagues. And he has shown off a quick wit with one-liners in nearly every interview.

"We talked about this very early in camp, how he was showing up with a new attitude, not using a translator," Cubs president of baseball operations Theo Epstein said. "He wanted to fully embrace his teammates and the organization and the fans and write a new script. That’s easier said than done, and he’s backed it up with his actions and [he] just looks like someone who’s more comfortable."

All of that is great for the Cubs, but what can they expect on the mound from Darvish? Based on Spring Training, the team can again expect a fastball that sits around 95 mph and reaches 97. They can expect those swing-and-miss sliders, along with the cutter, sinker and splitter. That is a potentially powerful arsenal to help give the Cubs' ball-in-play staff an arm that can miss bats.

What may not be realistic is expecting Darvish to throw 200 innings after logging only 40 frames in the Majors last season, which means that communication between the starter and new pitching coach Tommy Hottovy will be critical throughout the campaign. Having six off-days in April can help ease the early-season innings load for Darvish, but the Cubs will need to find other ways to play it smart as the summer progresses.

"You have to communicate. That's the biggest thing," Hottovy said. "I could sit here and plan everything out, but you don't know what's going to happen. You have to communicate with them, like, 'How do you feel? How are things progressing? Do you want to move the bullpen days around?' You have to be flexible. If you're not, I think the rigidity of the schedule causes more problems than just being able to have the fluidity of how you want to do your work and side days."

Perhaps one silver lining to last year's injury woes was that Darvish's absence led to the Cubs acquiring lefty Cole Hamels, who remains in the fold for 2019. Now, with Darvish healthy, Chicago's rotation is deeper, with Hamels, Jon Lester, Kyle Hendricks and Jose Quintana rounding out the staff.

That group will be key to the Cubs contending for a World Series again, and Darvish is arguably the most crucial piece of the puzzle. If this spring is any indication, he looks poised to move well beyond last year's problems.

"I know it's going to show out there this season," said Hamels, who was Darvish's teammate on the Rangers from 2015-17. "I think that's what everybody's waiting for. But I think that's what he’s ready to show people. For us, to be able to play off that, and to be able to pitch in front of him, behind him, wherever in the rotation it is -- I've done it before and I've enjoyed it, and I look forward to this year."