WEST PALM BEACH, Fla. -- Marlins fans in attendance for Sunday's Grapefruit League opener at The Ballpark of the Palm Beaches got their taste of in-person baseball for the first time in a year. They had barely gotten settled in their seats when they jumped right out of them as Jazz Chisholm, a key piece of the organization's highly regarded farm system, belted a leadoff homer. Lewis Brinson and JJ Bleday would also go deep in Miami's 6-1 win over Houston in seven innings.

"We all said when we scored the four runs in the first, 'Man, what a difference it is to have fans in the stands again,'" Brinson said on Zoom. "It feels great. They really make our game, and we're happy to have them back."

• Castano, Neidert pass first spring mound test

Some fans wore "Miami Bottom Feeders" T-shirts -- a reference to a Phillies broadcaster's shot at the underdog Marlins in 2020. During the first-inning rally, chants of "Let's Go Marlins!" could be heard echoing throughout the concourse on the club's "road" game.

Despite making the postseason for the first time in 17 years, most pundits have picked the Marlins to finish last in the National League East.

"We came out today and just try to show people that we're not bottom feeders, you know, they call us bottom feeders, but we're going to come out and swing our sticks, and we're going to be ready to face anybody," Chisholm said on Zoom. "We know we're in the hardest division in the league, and we're going to live up to the hype of the division. We're not just going to sit down and let everybody trample over us, so we're coming out hot."

Here are five storylines to watch this spring:

1) Second-base battle

Former MLB Pipeline Top 100 prospect Isan Díaz and Chisholm could be the organization's future middle-infield tandem. Until then, they are competing for the Opening Day second-base job as part of a veteran-led Marlins lineup. The pair has 76 Major League games between them.

The 23-year-old Chisholm, starting at shortstop with the club giving Miguel Rojas and the other veterans an extra day, wasted no time kicking off the battle with his leadoff homer to left field off Astros starter Brandon Bielak. Afterwards, Chisholm, ranked as MLB Pipeline's No. 66 overall prospect, said on Zoom that he told his teammates he would hit an opposite-field homer because he never leads off.

"It felt great to start off with a bang," Chisholm said. "Coming into Spring Training -- like I told you guys -- I've been working really hard, and glad to see that I showed it from the first at-bat."

Díaz, who went 0-for-2 at the plate, did start a nifty 4-6-3 inning-ending double play with Chisholm in the third. The 24-year-old, considered the Marlins' future second baseman when the club acquired him in the Christian Yelich trade, had a disappointing season in 2020. Miami's Opening Day starter at second, he elected to opt out after the COVID-19 outbreak before returning and then straining his left groin.

If Chisholm puts together a spring so impressive it can't be ignored, what happens to Díaz? Manager Don Mattingly said earlier in the week it would make sense for the other player to head to the Minors for consistent at-bats.

2) What can the kids do?

Ten of Miami's Top 30 prospects were on the travel roster for Sunday's spring opener. Leading the way was Bleday, who served as the designated hitter and lined a solo homer to left-center off of Astros right-hander Bryan Abreu in the fifth. 

Bleday recorded 151 plate appearances after being selected fourth overall in the 2019 MLB Draft. Invited to big league camp last year, he went 3-for-13 in limited action before COVID-19 shut down Spring Training. However, the 23-year-old outfielder was in the 60-man player pool in '20 and played at the alternate training site.

Without a Minor League season under their belts in 2020, these spring games will be a chance for the prospects to see game action and show what progress has been made. When the starters came out of Sunday's game, they were replaced by even more young guys: first baseman Lewin Díaz (No. 8 prospect), shortstop Nasim Nunez (No. 20), left fielder Peyton Burdick (No. 16) and right fielder Jesús Sánchez (No. 5).

"I think it comes right back when they start playing games," Mattingly said on Zoom. "Obviously, maybe a little bit [rusty] early. ... But I think it does take a little bit of time, the more games you play the more rhythm you get into."

3) Rounding out the rotation

Sandy Alcantara, Pablo López and Elieser Hernandez are locks for the Nos. 1-3 spots on the starting staff. Top prospect Sixto Sánchez, whose arrival to camp was delayed a couple days, is projected as the fourth guy. 

So who gets the last spot? 

Rookie lefty Trevor Rogers, who was originally delayed during the intake process, is with the club. The 23-year-old showed flashes in seven big league starts in 2020. Other candidates include Daniel Castano and No. 11 prospect Nick Neidert, who began their auditions on Sunday afternoon. Then there is Rule 5 Draft pick Paul Campbell (No. 25 prospect) and rookie lefty Braxton Garrett, who made two starts during doubleheaders in 2020. However, he only has one start at the Double-A level. MLB Pipeline's No. 68 overall prospect Edward Cabrera was a strong candidate until arriving to camp with an inflamed nerve in his right biceps.

"We're going to need all those guys through the course of the season," Mattingly said. "You do every year. We're going to have things that we'll be watching with all our guys all year long. So we're going to need all these guys."

4) Figuring out bullpen roles

It's no secret the Marlins made the relief corps a priority over the offseason. Much had been written and said about it. Miami signed Anthony Bass and Ross Detwiler as free agents, dealt for Dylan Floro, John Curtiss and Adam Cimber and acquired Campbell and Zach Pop via the Rule 5 Draft. Those newcomers joined returners Yimi García, Richard Bleier and James Hoyt.

Who will be the closer? 

Bass paced the Blue Jays with seven saves in 2020, while García pitched in plenty of big situations for the Marlins. Mattingly even said Floro, who wasn't used in high-leverage scenarios for the World Series champion Dodgers, could be used late.

Who is the long reliever? 

Curtiss was used in a variety of roles with the Rays and Detwiler is a former starter. Could a losing candidate for the rotation wind up in the bullpen?

Then there's the case of how many relievers will make the 26-man roster. Earlier in the week, Mattingly said the ballclub will likely go with 13 position players and 13 pitchers. If so, where does that leave Campbell and Pop, who must be on the active roster all season or be returned to their former clubs? 

5) Reps at first, outfield

Barring the last-minute addition of the universal designated hitter, Jesús Aguilar will get the brunt of work at first base and Garrett Cooper will see time in the outfield, where he has been practicing since reporting to camp. In Sunday's Grapefruit League opener, Cooper started at first base.

With Corey Dickerson, Starling Marte and Adam Duvall, the Marlins will field an all-veteran outfield. That leaves the next tier of guys -- Magneuris Sierra and Lewis Brinson -- fighting for the fourth spot. Jon Berti and Cooper provide versatility should the club not go with a fifth true outfielder. Prospects Monte Harrison and Jesús Sánchez, who debuted in 2020, could use more grooming in the Minors. Same goes for Jerar Encarnación, who arrived late to camp because of a visa issue. Finally, there are non-roster prospects like Bleday, Burdick, Kameron Misner and Connor Scott with varying estimated times of arrivals to the big leagues.