(CBS) The MLB Players Association has expressed concern over the Cubs’ lack of spending on players, according to a Chicago Sun-Times report published over the weekend. Despite playing in the nation’s third biggest market, Chicago’s payroll is around $90 million, a number that ranks in the bottom one-third of the sport.

The Cubs’ payroll has decreased in each of the past four years, according to Cot’s, as the franchise undergoes a complete rebuilding project, with a focus currently on developing young players instead of spending big in free agency.

More from the Sun-Times:

Sources said the union is concerned about how the Cubs’ business practices are affecting player markets. At least one agent met with Cubs chairman Tom Ricketts this year, according to sources, to make the case for investing in the major-league team even as the club overhauls the scouting and player development system.

Whether the most powerful players union in American sports can do anything about the high-revenue team’s years-long trend of spending cuts and roster purges is tricky. It might depend in part on how much longer it lasts and if the union can find grounds for action in Major League Baseball’s debt-ratio rules for clubs.

There is precedent for the league and union pushing teams to increase spending, as the Marlins were forced to do so several years ago. The difference in that situation and the Cubs’ is that the Marlins were receiving money from the revenue sharing system, while the Cubs pay into it. So it remains to be seen what, if any, action the Cubs could be forced to take.