JUPITER, Fla. -- The Marlins appear to have cleared up who will be in right field on Opening Day.

On Saturday, the club announced that Peter O’Brien has been optioned to Triple-A New Orleans, opening the door for Garrett Cooper in right field.

The organization does not plan to announce its Opening Day roster until the deadline on Thursday, before the Marlins face the Rockies at Marlins Park.

But sending O’Brien down is a strong sign that Cooper has won a roster spot, and he will get ample time in right field, and perhaps left. He also can play first base.

“It was easily our toughest decision,” manager Don Mattingly said. “A lot of factors went into it. When you make a decision like that, you don’t know if it ends up being the right one or not. But, we’ll find out. We had to make one. We had our meetings today.”

The decision is somewhat surprising because entering Spring Training, the Marlins appeared committed to O’Brien being on the club, and perhaps being their cleanup hitter.

For Cooper, making the Opening Day roster is story of perseverance. The 28-year-old was Miami’s starting right fielder in the 2018 opener, but he was struck by a pitch on his right wrist in the second game. The injury plagued him all season, and he had surgery late in the year.

Cooper player in 14 MLB games in 2018, and he had 38 plate appearances. This spring, he stepped up, hitting .421 entering Saturday night.

“It’s been a long road,” Cooper said. “Last year was something I’d never been through in my whole life. Especially sitting on the bench and having that mental aspect of having to grind through it. To get to the point where I am right now, and having such a good spring, it’s been a breath of fresh air for me.

"Coming off a whole year of getting [38 plate appearances], that’s not something a baseball player wants to go through, or any athlete, in general. I’ve worked my butt off over the offseason. I came in with the mindset of trying to win a job. It was a competition. It’s still out there. You take it day by day, whatever happens happens.”

A native of Hialeah, Fla., O’Brien opened eyes within the organization last September with a strong final month. As a callup, he hit .273 with a .338 on-base percentage, four home runs and 10 RBIs.

There’s no questioning the impact O’Brien can make when he connects. On 45 batted balls in play in September, his average exit velocity was 92.1 mph. But throughout his career, he’s dealt with a high volume of strikeouts and swings and misses.

O’Brien played in 18 Grapefruit League games, and he hit .220/.353/.390 with one home run, four doubles and 11 RBIs.

“We talk about the competition side of it,” Mattingly said. “It just ended up not going his way towards the end there. But it doesn’t mean he still doesn’t end up being a big part of our club.”

O’Brien picked things up after going hitless in 11 at-bats in February. In March, the 28-year-old hit .300/.450/.533.

At New Orleans, the Marlins are looking for consistency making contact.

“I think consistency with him,” Mattingly said. “Just consistency of contact. Putting the ball in play on a regular basis. He was getting better as camp went on. For sure, he was a little rough early. But I thought his at-bats got better.”

As the Marlins start finalizing their 25-man roster, Mattingly noted that rosters have a way of changing once the season starts.

“It’s one of the things we always talk about with guys,” Mattingly said. “Your club does not usually end up the way it starts. Usually, there are fairly major changes with your club as the season goes on.”