All have illustrated to a greater or lesser extent a lesson that has been apparent since Sydney's marquee man Dwight Yorke set up the only goal of the first A-League grand final to bring his team the first trophy.

For a team to be a success, it's all about the quality of its foreign signings.

Each A-League club is allowed five visa players, and historically those who have signed better-quality players who have been fit and able to play most of the games have done better in most seasons.

This year the trend is even more discernible.

Melbourne Victory coach Kevin Muscat has deservedly gained plenty of plaudits for bringing the club its first silverware in six seasons in the shape of the Premier's Plate.

He should also get plenty of bouquets for the quality of his overseas signings, as it is arguably those visa players who have made the difference between Victory finishing in the top four and it taking out the plate.

Fahid Ben Khalfallah has been the standout recruit of the year. The French-raised Tunisian international's skill, vision and competitive nature have given the Navy Blues an edge in the forward third in almost every match they have played this season.

Besart Berisha needs little introduction as he had been a star in Brisbane, but Victory had the cash and the chutzpah to tempt the Albanian south after he had won the title with the Roar last year.

Matthieu Delpierre, although injured for several months, has also been a huge addition. The tall Frenchman's calm presence at the back has stiffened Victory's defence during the crucial last month of the campaign, and having him there for the finals increases the Navy Blues' chances of taking their first championship since 2009.

Brazilian Gui Finkler and Kiwi Kosta Barbarouses were already there, but they have also been key factors in Victory's strong season.

Sydney has a similar tale to tell. Graham Arnold's marquee man, Marc Janko, heads the A-League golden boot table with 16 goals and the Austrian centre-forward has been the go-to man for one of the season's most prolific attacks.

Serbians Nikola Petkovic and Milos Dimitrijevic have also figured in the Sky Blues' run at the championship, with the latter, in particular, having a standout campaign.  Arnold believes that the addition of Jacques Faty and Mickael Tavares, the Senegalese defender and midfielder, have also been important components in his side's strong second half of the season.

It is a similar story in Wellington, where the foreign legion has had a huge impact and helped turn Ernie Merrick's side into one of the most attractive teams in the competition.

Dutch midfielder Roly Bonevacia has provided a mix of guile and steel in the centre of the park, while exciting Fijian Roy Krishna has impressed with his pace and sharpness in the front third.

Wellington have also been well served by their two Spaniards, Alex Rodriguez and Albert Riera, the latter surely one of the best stories to emerge in the A-League's history, the part-time footballer who backpacked his way to NZ and ended up as a full-time professional in a team chasing the championship.

Adelaide have their  band of strolling Spaniards and Latinos, highlighted by the highly skilled Marcelo Carrusca, the creative heartbeat of Josep Gombau's side. The former Albicelestes under-20 international is the man who makes the Reds tick, but he is aided and abetted by the likes of Sergio Cirio, Isaias and Pablo Sanchez, all Iberians who have given the South Australian side a distinctive flavour.

Even Glory, which won't play in the finals because of their salary-cap infractions, have hit the jackpot with their star overseas man Andy Keogh, even if it was extra payments to the Republic of Ireland striker that helped push them over the salary cap precipice. It was Keogh's workrate and goals, especially in the first half of the season, that helped propel Kenny Lowe's team to the top of the table for so long.

The evidence is clear: if you want to succeed, get your foreign scouting network in good order and sign the right overseas players. Too many clubs have recruited poorly and have paid the price. With five visa spots per club all foreign signings really should be members of the starting XI, barring injury or illness.