Question: What's rarer than a team producing a quality everyday player who becomes a lineup fixture for years to come? Answer: A team producing two of those players at roughly the same time.

Royals fans could be seeing the beginning of such a situation. On June 10, the team called up 22-year-old Mike Moustakas to play third base across the diamond from 21-year-old fellow top prospect Eric Hosmer. It's far too early to be making any proclamations, and early returns have been modest, but these two have the tools to become dual forces in the Royals' lineup for years to come.

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If both succeed and remain Royals for a long time, they will join a select group of position player tandems since World War II who debuted with the same team in the same or consecutive years. To be considered, both players also must have become regulars within a year of each other. This rules out Derek Jeter and Jorge Posada. Jeter played every day in 1996 while Posada got only a cup of coffee that year and was part-time the next. Here are the 10 best examples of the past 65 years:

10. Will Clark,
Robby Thompson

Giants. San Francisco fans might have gotten a sense of this pair's promise on opening day of the 1986 season, when Clark and Thompson both made their major league debuts at the Houston Astrodome. Clark homered and Thompson doubled off future Hall of Famer Nolan Ryan as the Giants won 8-3. Clark and Thompson proceeded to hold down the right side of the Giants infield -- Clark at first base, Thompson at second -- until Will the Thrill left for Texas in 1994. Combined Baseball-Reference wins above replacement (WAR) for Giants: 68.5

9. Jim Rice, Fred Lynn

Red Sox. Drafted two years apart, Rice and Lynn both made brief MLB appearances in 1974. In 1975, it's fair to say they nailed down starting jobs. Rice, playing left field and DH, finished second in AL Rookie of the Year voting and third in AL MVP voting. He had nothing on Lynn, who won both awards while racking up a .331/.401/.566 line and 7.1 WAR. Peter Gammons, then of the Boston Globe, nicknamed them the Gold Dust Twins. Rice won his own MVP in 1978 and went on to a Hall of Fame career, while injuries prevented Lynn from consistently playing to his potential. Combined WAR for Red Sox: 71.2

8. Ron Cey, Davey Lopes

Dodgers. Third baseman Cey and second baseman Lopes represent half of a Dodgers infield, along with Steve Garvey and Bill Russell, that remained intact for more than eight seasons, an MLB record. Both were rookies and immediate contributors in 1973 and helped lead LA to four World Series and one title between then and 1981. Cey was a solid hitter who posted an OPS+ of 125 in his 12-year Dodgers career. Lopes was a prolific and efficient base stealer, twice leading the league in steals and finishing his career with 557 thefts and an 83 percent success rate. Combined WAR for Dodgers: 75.3

7. Tim Raines, Tim Wallach

Expos. Both Tims logged their first sustained playing time during the strike-shortened 1981 season, Raines bursting onto the scene with a .304/.391/.438 line and a league-leading 71 stolen bases. Despite a well documented cocaine problem, Raines became one of the most dynamic players in baseball, combining excellent on-base skills with a little pop and blazing speed. He led the NL in steals each of his first four seasons, winding up with 808 with an 84.7 percent success rate in his career. Wallach, meanwhile, was a solid all-around player who made five All-Star teams and won three Gold Glove awards in 13 seasons in Montreal. Combined WAR for Expos: 77.8

6. Reggie Jackson,
Sal Bando

Athletics. Jackson and Bando both experienced their first extended playing time in 1967, the Athletics’ final season in Kansas City. In a sign of things not to come, they both hit less than .200 with a sub-.600 OPS. With Jackson in the outfield and Bando at third base, Oakland enjoyed a tremendous run of success in the 1970s, including three straight World Series wins in 1972-74. Although Bando’s offensive numbers look muted because of the era during which he played, he registered a 127 OPS+ in his Oakland career and three times finished in the top five in AL MVP voting. Jackson won the award in 1973, when he led the league and home runs, RBI, runs scored, slugging percentage and OPS. Combined WAR for Athletics: 101.7

5. Duke Snider,
Roy Campanella

Dodgers. You might have heard of the Dodgers' premiere rookie in 1947, Jackie Robinson. Snider also debuted that season but struggled in limited action and did not take over as the Brooklyn starting center fielder until August 1948. A month earlier, the Dodgers had called up Campanella and installed him in the everyday lineup at catcher. Snider and Campanella remained in their roles until Campanella's career came to a tragic end when he was paralyzed in a car accident before the 1958 season. Both players became Hall of Famers and helped the Dodgers qualify for five World Series and win once, in 1955. In just 10 seasons, Campanella won three MVP awards (one of them narrowly and controversially over Snider), set a longstanding record (since broken) for homers in a season by a catcher and is third in MLB history in career caught stealing percentage. Snider is eighth all-time among center fielders in WAR. Combined WAR for Dodgers: 102.7

4. Frank Thomas,
Robin Ventura

White Sox. Talk about savvy drafting. The White Sox selected Ventura and Thomas with their first round pick in consecutive years (Ventura 10th overall in 1988, Thomas seventh overall in 1989). Ventura received a September call-up in '89 and took over as the team's starting third baseman in '90, with Thomas getting promoted for good that August and stuck at the opposite corner. They remained on the South Side together until through 1998. Sadly yet amusingly best known as Nolan Ryan's punching bag, Ventura was a stellar hitter and fielder, while The Big Hurt established himself as one of the game's premiere and certainly most menacing offensive threats. From 1991 to 1997, Thomas led the AL in walks, OBP and OPS four times each, registered three 40-plus homer seasons and snagged a pair of MVP awards. Combined WAR for White Sox: 109.4

3. George Brett,
Frank White

If Hosmer and Moustakas want an example from their own franchise, they can look at this pair. Both debuted in the summer of 1973, with White gradually getting more playing time over the next few years and Brett taking over the starting third base job in 1974. Brett became one of the top third basemen of all time, collecting 3,154 hits, a 135 OPS+ and better than 300 home runs while playing his entire 21-year career in Kansas City. In 1980, he batted .390 with a 203 OPS+ and won the AL MVP award. White resided on the other end of the offensive spectrum, batting .255/.293/.383 for his career. But he also was a supremely slick fielder at second base, winning eight Gold Gloves and saving 121 runs with his fielding in his 18 seasons with the Royals. Together, Brett and White appeared in nearly 2,000 games together and won a World Series in 1985. Combined WAR for Royals: 111.9

2. Ron Santo, Billy Williams

Cubs. These two Cubs legends spent a combined 30 seasons at the Friendly Confines. Williams actually debuted first, in 1959, but did not become a regular until the start of the 1961 season, when he was the NL Rookie of the Year. Santo signed with Chicago as an amateur free agent as a 19-year old in 1959, made the majors in June 1960 and never looked back. He fought through diabetes to put up one of the best careers ever for a third baseman, although he was shamefully snubbed from the Hall of Fame. From 1964 through 1967, Santo was just behind Willie Mays for best WAR in baseball, was third in OBP and fifth in OPS. Williams twice finished second in MVP voting, including 1972, when he led the majors in slugging percentage and was second in OPS. Although the Cubs never made the postseason during this duo's tenure, it certainly wasn't their fault. Combined WAR for Cubs: 123.7

1. Alan Trammell,
Lou Whitaker

Tigers. It's hard to imagine two players more closely linked than Trammell and Whitaker. Drafted in back-to-back years, they first teamed in Double-A Montgomery in 1977 and were called up together to debut on Sept. 9 that year against the Red Sox. Whitaker started at second base and went 3-for-5; Trammell went 2-for-3 as the starting shortstop. In 1978 they were both everyday players at those positions, Whitaker winning AL Rookie of the Year and Trammell finishing fourth. They went on to become baseball's longest-running double play combo, both playing their entire careers with the Tigers, a combined 4,683 games. This does not even include teammate Lance Parrish, who debuted four days before Trammell and Whitaker and was worth 27.5 WAR in 10 seasons with Detroit. Combined WAR for Tigers: 136.6

-- Andrew Simon writes the "Hitting The Cutoff Man" blog on Follow him on Twitter