According to the Pittsburgh Pirates, star outfield prospect Gregory Polanco isn't ready for the major leagues yet. Apparently, however, he's more than ready for a contract that could span a decade.

The Pirates recently offered the 22-year-old Polanco a seven-year deal with three club options that would guarantee him a little bit less than $25 million, a source with knowledge of the team's plans told Yahoo Sports. Polanco rejected the deal and remains at Triple-A Indianapolis, a casualty of Major League Baseball's service-time rules that continue to give teams an incentive to bury some of the best prospects in the minor leagues until June.

Pittsburgh's tack with Polanco mirrors a trend of offering the best up-and-coming players long-term major league contracts before their debuts. While no player has signed such a deal, the Houston Astros proposed a multiyear deal for outfielder George Springer during spring training. When he turned it down, the Astros kept him in the minor leagues for the first 2½ weeks of the season, delaying his free agency by a year.

The situation with Polanco is even more naked. At 12-20, with a .687 team OPS and failing platoon in right field, the Pirates unquestionably could use Polanco, who is hitting .397/.449/.621 with four home runs and 26 RBIs. Between his performance over the season's first month and his MVP showing in the Dominican Winter League, he has solidified his place among the top echelon of prospects – the sort whom teams conspire to keep in the minor leagues until after the projected cut-off for so-called Super 2 players.

The top 22 percent of each service class are designated Super 2 players, meaning they are granted arbitration – and therefore a higher salary – for four seasons instead of three. By keeping a player in the minor leagues until after the Super 2 cut-off, which is usually in early to mid-June, teams estimate a savings of millions of dollars.