Monday marks Opening Day for Major League Baseball's 2017 season, one that begins a little more than four months after the league and its players signed a new collective bargaining agreement. The five-year deal, which guarantees play uninterrupted by labor strife, also generated a healthy amount of billings for outside law firms advising the Major League Baseball Players Association.

The New York-based labor union, one of the most powerful bodies in professional sports, had more than a dozen legal advisers on its payroll in 2016, according to the organization's annual LM-2 filing with the U.S. Department of Labor on March 31. The document covers the period between Jan. 1, 2016 and Dec. 31, 2016. Sidley Austin and Francisco-based litigation shop Altshuler Berzon took the top two spots in the legal fee standings, billing $346,222 and $221,328, respectively, for their work on behalf of the MLBPA.

Sidley litigation partner Virginia Seitz in Washington, D.C., a former head of the U.S. Department of Justice's Office of Legal Counsel who returned to the firm in late 2014, has been a longtime legal adviser to the union. The MLBPA's LM-2 filing shows that Sidley had a key role representing the union on its labor negotiations with the league, receiving an assist from Altshuler Berzon, which also continued in its role handling litigation work for the union.