There are three Grapefruit League games remaining following the Nationals’ 7-3 loss against the Marlins on Thursday night. Between now and Opening Day on April 1, the Nats have roster decisions to make -- not just who will make the team, but where they will play. Take a look at four decisions facing Washington as it nears the end of Spring Training action:

• Starting third baseman

The starting third base job still is up for grabs. While it has been Carter Kieboom’s to earn, manager Dave Martinez wanted to explore the option of starting second baseman Starlin Castro at the hot corner. That experiment has been brief since Castro exited Tuesday’s game -- his first of spring at the position -- in the seventh inning. An MRI revealed a mild left hamstring strain, and Castro is day-to-day. The Nats have depth at third they can tap into for the remainder of camp, including Josh Harrison, Jordy Mercer and Hernán Pérez.

“We’ve still got a few days,” Martinez said. “We hope to get [Castro] back soon. But these guys will all get the opportunity to play in the infield.”

• Leadoff spot

Even though Victor Robles has been thriving in the leadoff spot, Martinez could see a benefit of him returning to the bottom of the order. On Thursday, Martinez bumped Trea Turner up to leadoff and moved Robles behind opener Luis Avilán, who hit eighth.

“This is not really set in stone,” Martinez said.

Martinez had a conversation with the starting center fielder on Wednesday, and he told him the new look didn’t have anything to do with his performance. This spring, Robles is batting .273 with a .944 OPS and three homers in his first 16 games. Having Turner hit after Robles adds speed and base-stealing potential to the lineup and presents opportunities for Juan Soto to drive in runs behind them.

“It’s more about getting Robles to hit ninth in front of Trea and Soto,” Martinez said. “If we do it this way, I look at that nine-hole hitter as being a second leadoff guy, potentially.”

• Possibility of an opener

The Nationals are cognizant that two of their potential five starters have not seen extensive action in over a year. Fifth-starter frontrunner Joe Ross elected not to play in 2020, and Stephen Strasburg threw only five innings last season before undergoing surgery for carpal tunnel neuritis in his right hand. With that in mind, the Nats could utilize an opener.

“My concerns are building up so many innings with these guys early on,” Martinez said. “This is a possibility that we’re looking at -- maybe giving them an extra day, maybe going bullpen day, things of that nature, maybe having somebody else spot start and then having to use the bullpen. So, we’re looking at all these different options. I want to be prepared for anything because you never know.”

The Nationals have candidates should they go this route, including veterans Paolo Espino and Avilán, who got the nod on Thursday. Avilán, 31, has tossed 349 innings of relief with a 3.30 ERA over his nine-year career. He had not started since his Minor League days.

“It doesn’t matter what inning it is or who you’re facing,” Avilán said after allowing a pair of walks and a run over two hitless frames. “It’s not like in the first inning I’m going to start throwing knuckleballs or something like that. It’s the same game. … I’m just ready for whatever the chance might be.”

• Fourth outfielder

A big criteria for the Nationals’ fourth outfield spot is the ability to play all three positions. Andrew Stevenson has emerged as the top candidate. Washington still is monitoring the progress of Gerardo Parra. The 2019 World Series championship spark plug has been working his way back from right knee surgery. Martinez approximated Parra is “85, 90 percent.”

“On occasion, I do see him limp a little bit as he’s running, so we want to be very cautious,” Martinez said. “He’s getting there. He’s getting his at-bats, he’s starting to swing the bat well, but we want to make sure that he’s completely ready …

“I have a very soft spot for him, what he does in our clubhouse. I love him as a player. He does a great job pinch-hitting. But he also understands that he’s got to be able to play center field as well, so that’s something that we’re working towards.”