JUPITER, Fla. -- It wasn't even noon, but Jose Fernandez was firing unhittable pitches like clockwork. What a great way to start the day.

This was on a back field on the Marlins' side of the Roger Dean Stadium complex, in a simulated game designed only to get some work for Fernandez and a few other pitchers. But the chance to watch Fernandez lured All-Star teammate Dee Gordon and fellow Marlins starters Tom Koehler, Jarred Cosart and Brad Hand to the metal bleachers ringing the infield.

"That was great," Fernandez said. "The relationship we have going on with the pitchers, the players. That's really good stuff. I think that's what it takes for a team to come together. Little things like that mean a lot."

• Spring:Tickets | Ballpark | 40-man roster | NRIs

So do the big things, like potentially getting full seasons from Fernandez and Giancarlo Stanton. Miami hasn't had its two best players healthy at the same time since a game in San Diego on May 9, 2014.

One or the other of them was on the disabled list -- and sometimes both of them -- for the past 288 games. But aside from the recent uncertainty surrounding hop-and-a-skip reliever Carter Capps, the Marlins head toward the 2016 season healthy. That's maybe the biggest reason that they shouldn't be overlooked in a top-heavy National League East.

Here are five other reasons the Marlins are arguably baseball's best sleeper team:

1. Fernandez is prepared to jump back into the discussion of the NL's best pitchers.

Fernandez has survived both 2014 Tommy John surgery and a shoulder scare from last August, and he is ready to once again be a no-hitter waiting to happen every time he takes the mound. He struck out five of the seven hitters he faced in the simulated game on Wednesday morning, throwing high-90s fastballs to both sides of the plate while sprinkling in some sliders and changeups.

Fernandez had a smile on his face both before and after the workout.

"That's him," said Jack McKeon, the longtime manager who serves as a special assistant to Marlins owner Jeffrey Loria. "It doesn't matter if it's out here in the morning or on Opening Day. He's the same guy. He's special."

Fernandez was only 20 years when he came to the big leagues in 2013. He was 12-6 with a 2.19 ERA that season, winning the NL Rookie of the Year Award and finishing behind only Clayton Kershaw and Adam Wainwright in the NL Cy Young Award voting.

"Just lucky, man," Fernandez said. "Lucky and blessed to be out there."

The Marlins will monitor Fernandez's innings carefully this season, with 180 viewed as the same kind of soft cap it was for Matt Harvey last season. They'd love to have to figure out what to do with him in the postseason.

2. The arrival of Don Mattingly and other newcomers -- especially pitching coordinator Jim Benedict and hitting coach Barry Bonds -- has energized an organization that seemed to lose its direction last season.

Mattingly has never had a losing season as a manager, guiding the Dodgers to a 446-363 regular-season record over the past five years before a mutual parting of ways after the Mets beat the Dodgers in the NL Division Series last October.

Mattingly is taking over a team that is loaded with a set lineup with only one starting position player -- third baseman Martin Prado -- in his 30s. His message to Marcell Ozuna, Christian Yelich, Justin Bour, Adeiny Hechavarria and J.T. Realmuto (among others) is that it's one thing to be a big league regular, and another to be a major contributor on a postseason team.

"One year they have success," Mattingly said about younger players. "If you don't keep working, the league works on you, and there's going to be a bounce-back the [wrong] direction. So you have to continue to try to improve. That's really going to be our key to success -- can we get better? Are we going to get better as a young team with potential?

"We see a lot of talent, lot of potential, [but] are we going to kind of continue to improve and improve and improve? If we can, we're going to be a really good club."

3. The Marlins can really catch the ball.

Gordon, who was a force as a leadoff man after being acquired from the Dodgers, won a Gold Glove Award at second base last season. Yelich won one in left field in 2014. Hechavarria is the total package at shortstop, but he has thus far been bypassed for the Gold Glove Award -- won by Brandon Crawford in 2015 and Andrelton Simmons in '13 and '14.

The Marlins ranked third in the Major Leagues with 37 Defensive Runs Saved last year, behind only the D-backs and Royals.

4. Stanton is the best bet in the NL to take the MVP Award away from Bryce Harper.

Stanton hasn't played 150 games in a season since 2011, but he is at full speed this season. The slugger had surgery on his left hand last June and figures to benefit from not returning to play some inconsequential games in September, as he has had a full recovery.

Stanton was hitting only .265 when he was sidelined, but he had 27 home runs and 67 RBIs in 74 games before going out. He could benefit from the emergence of the late-blooming Bour, who hit 23 home runs as a 27-year-old rookie last season.

Bonds has made Ozuna his top project this spring, and early results are encouraging. Gordon and Prado should provide Stanton the chance to drive in a lot of runs.

5. Wei-Yin Chen will be a difference-maker for the rotation.

The Marlins invested $80 million over five years to sign the 30-year-old lefty from Taiwan in the offseason. It was the sixth-biggest contract for a free-agent pitcher this past offseason, and it could prove shrewd.

Chen has been embraced by Fernandez, who started studying video of his new teammate shortly after Miami signed Chen.

"I'm a baseball fan," Fernandez said. "I went and looked at a couple games -- what he's done, how he pitches, what he likes to do. I've talked to him this spring. We've become good friends."

Chen was the Orioles' best starter last season (11-8, 3.34 ERA), and he could benefit from moving to the NL. Chen lengthens the rotation that includes Koehler and Cosart, with Edwin Jackson, Justin Nicolino, David Phelps and Hand in the mix for the fifth starter's spot.