Every once in a while, a prospect arrives in Portland and creates a buzz around Hadlock Field and throughout Red Sox Nation.

In 2004, it was Hanley Ramirez, a 20-year-old from the Dominican Republic. Ramirez arrived as Boston’s top prospect, though he was traded after the 2005 season and went on to win Rookie of the Year honors and a batting title while with the Marlins.

In 2012, it was another shortstop, Xander Bogaerts, then 19, a rare prospect from Aruba. He also was a No. 1 Red Sox prospect. He arrived Aug. 9, and was starting in the World Series the next year. He now leads the American League in batting (.352).

Now, in 2016, we have the arrival of second baseman Yoan Moncada, another No. 1 Red Sox prospect and the third-best prospect in all the minors, according to Baseball America.

Moncada, 21, will be in a Sea Dogs uniform for the first time at 7 p.m. Tuesday when Portland begins a six-game homestand against Harrisburg.

So what is the big deal about Yoan Moncada? Glad you asked.

Q: Why is Moncada already well known?

A: The immediate answer is $63 million. That was the well-publicized amount the Red Sox paid to sign Moncada on March 12, 2015, when he was a 19-year-old free agent, recently arrived from Cuba. That sum included a $31.5 million bonus, which was $26 million more any previous signing bonus for an international free agent.

The other $31.5 million was paid in a fine to Major League Baseball because Boston had exceeded the MLB limit for international bonuses.

Q: OK, so he’s rich. Can he play?

A: Obviously, the Red Sox think so. They first noticed him playing in an international youth tournament in Mexico when he was 15. Moncada, now 6-foot-2, 220 pounds, is considered a five-tool player. He’s also a switch-hitter.

Q: What has Moncada done so far?

A: Moncada began playing in low Class A Greenville last year. After a slow start, he batted .310 in the second half of the season, with a .915 OPS (combined on base percentage and slugging average).

In Class A Salem this year, Moncada was batting .307/.923 in 61 games before his promotion after Sunday’s game.

Among all minor leaguers, he ranks first in stolen bases with 36 (in 44 attempts), second in runs (57), fourth in doubles (25), eighth in walks (45) and eighth in on-base percentage (.427). Moncada also has three triples and four home runs.

Q: What does he need to work on?

A: He can always improve his defense. The knock on Moncada was that he could make the sensational play, but sometimes struggled with the basics. He made 23 errors in 71 games in Greenville. This year, that number is down to 11 errors in 58 games.

Offensively, Moncada is raking left-handed (.315/.971), but his right-handed numbers were low but have improved to .286/.797.

Q: Will he stay at second base?

A: No. That’s the short, easy answer since Boston already has a major league second baseman, Dustin Pedroia, signed through 2021. Where will Moncada play – and when? – are the mysteries. In Portland, we may see Moncada play other positions. The guesses are third base and left field.

Q: Will Boston rush him to the big leagues?

A: No. Despite his massive signing bonus, Moncada is like other prospects coming up through the system and can spend years in the minors. The Red Sox don’t have to put him on their 40-man roster until after the 2018 season, although that is likely to happen sooner.

With so much invested, Boston will want control over Moncada’s services for as long as possible.

Moncada is in Portland because he was no longer being challenged adequately at the advanced Class A level. The same will go for Double-A. Once he shows he’s ready to move on, he will head to Triple-A Pawtucket.

Q: When can we expect Moncada in the majors?

A: Some have speculated by the end of this year. But, realistically, later in 2017 is a better bet, assuming he keeps progressing.

Q: Did the Red Sox gamble on Moncada?

A: Of course it’s a gamble, especially with Cuban players, who are not as thoroughly scouted. Boston signed Rusney Castillo to a seven-year, $72.5 million contract (including a $5.4 million signing bonus). Castillo, who turns 29 next month, has been a bust and was recently removed from the 40-man roster and sent to Pawtucket.

Q: What about the two pitchers promoted along with Moncada?

A: Starting pitcher Jalen Beeks, 22, was a 12th-round draft pick out of the University of Arkansas in 2014. A left-hander, Beeks was 4-4 in Salem, with a 3.07 ERA and 1.35 WHIP (walks/hits per innings).

Right-handed Ben Taylor, 23, was a seventh-round draft pick last year out of the University of South Alabama. He started in Greenville last year and for three starts in Salem this season, before moving to the bullpen as a long reliever. As a reliever, Taylor has a 1.69 ERA, 0.78 WHIP and 44 strikeouts/seven walks in 32 innings.

Q: Who else can Portland expect from Salem?

A: Shortstop Mauricio Dubon is playing for the Carolina League All-Stars. It’s feasible he could move to Portland from there. Dubon, 21, already has 124 games in Salem, including 62 this year (.306/.766).

Third baseman Rafael Devers, 19, is among Boston’s top positional prospects, along with Moncada and outfielder Andrew Benintendi. After a slow start, Devers is batting .339/.782 in June.

Left-handed pitcher Trey Ball, who turns 22 next week, was a first-round draft pick in 2013 (seventh overall). Ball pitched in Salem all last season (4.73 ERA) and is back with better numbers (2.60) in 10 starts.

Elsewhere in the minors …

TRIPLE-A PAWTUCKET is enjoying the production of two pitchers promoted from Portland. Since Aaron Wilkerson came up May 28, he is 3-1 with a 1.37 ERA, and 32 strikeouts and just five walks in 261/3 innings. Justin Haley made his Triple-A debut last week – eight innings, three hits, one run, seven strikeouts and one walk.

CLASS A GREENVILLE saw a hiccup from pitching prospect Anderson Espinoza last week when he allowed six earned runs in four innings. Espinoza, 18, is 4-5 with a 4.06 ERA, and 57 strikeouts and 21 walks in 572/3 innings.

Infielder Michael Chavis came off the disabled list June 7 (thumb) and went right back to hitting. Chavis, 20, is batting .326/.897 in 25 games.

SHORT-SEASON LOWELL began play last Saturday with right-handed prospect Michael Kopech on the mound for his 2016 debut. Kopech, 20, was another first-round pick in 2014 (the extra pick was compensation for Boston losing Jacoby Ellsbury to free agency). Kopech has had troubles – PED suspension last year, a broken hand during a fight in spring training – but he has crazy potential with a fastball in the high 90s and impressive secondary pitches. Kopech pitched 41/3 scoreless innings, allowing four hits and four walks, striking out four.