JUPITER, Fla. -- Following his third and final Grapefruit League start on Thursday night, Marlins top prospect Sixto Sánchez acknowledged he needs just a little more time to be ready for the season.

Sánchez, who threw 61 pitches across 3 1/3 innings in Miami's 7-3 win over Washington at Roger Dean Chevrolet Stadium, will take the mound again on Tuesday in some capacity. Whether that will be enough to convince the ballclub to put him in the Opening Day rotation is to be determined. The roster must be set at noon on Thursday, with first pitch scheduled for 4:10 p.m. ET against the Rays at Marlins Park.

"I think that after that start on Tuesday, I can be ready to be in the five-man rotation," Sánchez said in Spanish during a Zoom call.

The Marlins have consistently stated they want Sánchez to be built to at least 75 pitches or five innings before starting a regular-season game. Right-handers Sandy Alcantara, Pablo López and Elieser Hernandez will have thrown in a game setting at least six times this spring -- the last being a backed-down tuneup. Southpaw Trevor Rogers, who got a late start at camp, will have five outings under his belt.

Miami will not rush Sánchez, who had been eased into a spring routine his first two years with the organization. With the return of a 162-game season in 2021, he will have an innings limit. Despite that, the Marlins have a plan in place for MLB Pipeline's No. 15 overall prospect to pitch into September. His single-season career high for frames is 114 in '19.

"We're going to keep building him, and it's one of the things that we're going to make sure we do it safely," Marlins manager Don Mattingly said during a Zoom call. "I'm assuming that he's going to come out of this fine, and make sure -- with Sixto, we always talk about we would give him the extra day if he needed it. He hasn't needed it to this point. He's building and seems to be effective. So, we just kind of read the situation with him and then go from there."

Sánchez, who entered Spring Training projected to make the Opening Day rotation, was delayed getting to camp from the Dominican Republic because of visa issues. He also had a false COVID-19 positive test that set him back a couple of days waiting for results. The 22-year-old righty, who was 3-2 with a 3.46 ERA last season, didn't make his Grapefruit League debut until March 15.

Over three spring outings, Sánchez threw eight innings. On Thursday, facing most of the Nationals' expected Opening Day lineup, he fanned his first three batters of the spring and allowed his first run, while also walking and hitting a batter. In a scoreless first, Sánchez needed 24 pitches, 11 to Juan Soto, who worked a walk after falling behind 0-2 in the count. Twice he fouled off 100-plus-mph pitches. Sánchez's first strikeout came on a 90.9 mph changeup to Ryan Zimmerman -- the 18th batter he had faced in Grapefruit League play.

He bounced back with a 12-pitch second, then encountered trouble in the third by hitting the leadoff batter and giving up a ground-rule double. After consecutive defensive gems, Zimmerman sent a single up the middle to drive in a run. In the fourth, Sánchez recorded an out before being pulled following a double.

"All the pitches were working pretty much for me: my fastball, slider, cutter, and my changeup, too," Sánchez said via an interpreter. "I will say, most important part was I was throwing strikes. That was something that helped me a lot, and I was feeling even better than my last start."

If Sánchez is deemed not ready, right-hander Nick Neidert, Miami's No. 12 prospect, could take that Opening Day rotation spot. He gave up one run over four innings as the third Marlins pitcher on Thursday, lowering his WHIP to 1.11 and ERA to 2.84. All five of his spring outings have been in relief, though he built up his pitch count to 54.

The Marlins will have two off-days within the first nine dates of the season on April 4 and 9, but the club intends to begin with a five-man rotation as part of its long-term plan to monitor the young starters' innings, Sánchez included. Mattingly, who noted that Marlins brass will meet on Friday to discuss decisions, will need more than five starters over the course of a season.

"You just make decisions based on what you think and where everybody is at the time, so we'll get to those," Mattingly said. "Again, we're going to need all these guys. I think that's the one thing we get away from. When we get these last thoughts, we really tend to think about, you know who makes the club, who doesn't. But at the end of the day, we're going to need all these guys. They're all part of the same group."