Wellington Phoenix coach Ernie Merrick believes the A-League should abolish the salary cap as the competition enters it's 12th season.

Merrick is of the opinion that the new rules regarding guest players have made the cap redundant, saying the league is now stable enough to progress without it.

"I just don't know why we bother with a salary cap, I think we've grown up, it's been 10 years now, let's just get on with it," Merrick said.

"I don't know if it is a salary cap anymore, because there is a certain amount you can spend within the cap, then there are all these special little loyalty bonuses and first-year player bonuses - there are that many I have lost track - and then on top of that you can now really sign three marquee players."

The salary cap currently stands at a maximum of A$2.6 million, although marquee players and guest players don't have their salaries counted to the overall total.

Homegrown players, long serving players and even mature age rookies and youth players all have special salary cap rules, with certain portions of their deals not being included.

"Why worry about a salary cap?," Merrick said.

"Why not let people invest big? It just makes the league grow rapidly. That's what's happening in the MLS (in the US).

"I think it would present more of a challenge to our club to recruit well economically, to develop players, to have an academy where you're bringing players through and I think the challenge and the pressure is good for everyone."