The Pirates and Marlins quietly worked out a seemingly uneven trade last month that was arranged because Pittsburgh demanded compensation in exchange for allowing highly regarded special assistant Jim Benedict to take a job with Miami, multiple sources told ESPN.com.

The deal, which was announced Oct. 24, sent one of the Marlins' top pitching prospects, right-hander Trevor Williams, to Pittsburgh in exchange for right-hander Richard Mitchell, whom several scouts described as a non-prospect.

Williams, 23, went into last season ranked as Miami's No. 6 overall prospect and No. 4 pitching prospect, according to ESPN's Keith Law.

Neal Huntington (above) has built the Pirates into one of baseball's most successful organizations with the help of aides like Jim Benedict, who left Pittsburgh for a job with the Marlins last month. Jared Wickerham/Getty Images

The trade was announced one day after the Marlins hired away Benedict to be their vice president of pitching. Benedict was one of Pirates general manager Neal Huntington's most trusted aides, but also is regarded as being among the sport's top pitching gurus.

Benedict, along with pitching coach Ray Searage, has played a pivotal role in the Pirates' recent success in acquiring struggling pitchers such as Francisco Liriano and Mark Melancon, then making adjustments that turned around their careers. With Miami, Benedict will have similar, but expanded duties, which would include input into the draft and overseeing pitching development throughout the Marlins' organization.

In recent years, as the Pirates have grown into one of baseball's best organizations, their front office has allowed several executives to leave for promotions with other teams. However, the Pirates initially balked at allowing Benedict to depart for two reasons, according to industry sources: he was still under contract, and the club had already permitted one high-ranking executive, Marc Delpiano, to take a job with the Marlins late in the regular season.

Executives with several teams told ESPN that it is regarded as common practice for clubs to allow no more than one executive to take a job with another team, in order to protect themselves from being "raided" by the same team.

So while the Pirates didn't stand in Delpiano's way when he departed for Miami, they were hesitant to allow Benedict to follow him.

Eventually, the teams negotiated what appears to be a lopsided trade as a form of compensation, but never announced that the deal was tied to Benedict's departure. Benedict spent seven seasons with the Pirates, in a unique role that involved major league advance scouting, along with his work with pitchers at all levels of the organization.

He had previously worked for the Cleveland Indians, New York Yankees, Los Angeles Dodgers and Montreal Expos.

Williams, the Marlins' second-round draft pick in 2013, is 15-19 with a 3.35 ERA in three minor league seasons and last week pitched a scoreless inning in the Arizona Fall League's all-star game.

Mitchell, 20, was signed by the Pirates out of Columbia in 2012, but still has not progressed beyond the short-season Gulf Coast League. He pitched in just 10 games in relief this summer for the Gulf Coast Pirates and was scored on in six of them.