The A-League's wealthy clubs loom as the biggest winners from a raft of new salary cap and squad concessions unveiled by Football Federation Australia.

The changes come into immediate effect and will give clubs more flexibility than ever before in recruiting and retaining players, but also open up ample opportunities for expenditure outside the salary cap.

The most significant shifts involve the marquee and guest player rules, which have been loosened to make it easier for A-League clubs to sign big-name stars in the vein of Alessandro Del Piero, Shinji Ono and Dwight Yorke.

Clubs are still permitted two marquee slots but these can now be allocated to players of any nationality, instead of the previous rules whereby at least one marquee had to be Australian.

The guest player rule, which brought David Villa to Melbourne City for a hyped-up four-game stint last season, has also been changed with the maximum stint for a guest player increased from 10 to 14 weeks.

Guest player salaries remain unregulated.

Hypothetically, this could allow City to borrow Andrea Pirlo, Frank Lampard or Villa from sister club New York City FC when Major League Soccer concludes for a period of close to half an A-League season.

Meanwhile, the much-speculated veterans' allowance is now a reality. A new 'loyalty player allowance' gives clubs a sliding scale of salary cap relief for players who have played "between 5-10 years at the club", up to $200,000 outside the salary cap.

"The Player Contract Regulations changes offer significantly increased salary opportunities for players as well as providing flexibility and rewards for clubs who plan their roster around Marquee Players, youth development and long term loyalty to its players," A-League chief Damien de Bohun said in a statement.

"These changes will allow clubs to bring talented players through their expanding youth systems, retain cult heroes like Melbourne Victory's Archie Thompson and continue to search for Marquee and Guest Players that can add impact to the continued growth of the Hyundai A-League."

Other changes include a salary cap 'banking' system that allows clubs to carry-over money not spent in the cap for two seasons to the following season, while each club can now sign a mature-age rookie outside of the cap in a move designed to highlight the dormant talent at state-league level. - AAP