After the longest preseason in football, the battle for the Toilet Seat finally returns. The boardroom struggle for control means season 2019-20 is one of transition for the A-League, while a lack of blockbuster signings underlined the more subdued lead-up.

Still, there are plenty of talking points. A new club and another on the way, and coaching changes to rival the player merry-go-round.

Here's all you need to know about every team ahead of Friday night's opener between Adelaide United and Sydney FC.

JUMP TO: Adelaide United | Brisbane Roar | Central Coast Mariners | Melbourne City | Melbourne Victory | Newcastle Jets | Perth Glory | Sydney FC | Wellington Phoenix | Western Sydney Wanderers | Western United

Last season: 4th

Key additions: Riley McGree (Melbourne City), Kristian Opseth (Erzurumspor), James Troisi (Melbourne Victory), Michael Maria (Charlotte Independence)

Key losses: Craig Goodwin (Al-Wahda), Scott Galloway (Melbourne City), Isaias (Al Wakrah)

At a glance: Adelaide's FFA Cup run has provided a positive enough starting point. Considering the departures of Isaias and Goodwin, though, the beginning of the era under new director of football Bruce Djite was arguably characterised by underwhelming transfer activity.

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Bringing Troisi back to his home state of South Australia could appease some fans after three defining years with Melbourne Victory. For all his asphyxiation of play on the pitch, Isaias almost became the sole point of contact with the referee as time progressed and players moved on. Watching a dressing room find its voice amid that wake will be one of the more interesting subplots this season. As a consequence, McGree's ceiling could also become much clearer this term.

Player to watch: Ben Halloran. Remains the Reds' most important player in phases of possession. Deployed in a number of positions under previous manager Marco Kurz, who was able to do that because of Halloran's movement. Continuity might see the 27-year-old improve further.

Rahmat Akbari could prove to be a savvy addition to Brisbane Roar's midfield. Jono Searle/Getty Images

Last season: 9th

Key additions: Jay O'Shea (Bury), Aaron Amadi-Holloway (Shrewsbury Town), Brad Inman (Rochdale), Roy O'Donovan (Newcastle Jets)

Key losses: Eric Bautheac (Omonia Nicosia), Alex Lopez (Racing Ferrol), Joe Caletti (Floro SK), Matt McKay (Retired)

At a glance: Last season for Brisbane can be concisely summarised: Good individuals, bad team. Darren Davies slowly losing his mind on the touchline as the Roar were continuously carved open in transition made for an entertaining but unpretty watch. Whatever happens under new coach Robbie Fowler, even in the worst case scenario, the Roar's healthier average age should at least translate to a less porous midfield.

Fowler grasping the process of coaching on the fly will be an interesting case study for the A-League and Australian football as a whole, given the continuously defined ceiling for the majority of coaches at NPL level and below. O'Donovan is a known quantity in the A-League, for better and worse, and can be effective given adequate service.

Player to watch: Rahmat Akbari. Brimming with talent but received next to no minutes under both previous Roar coach John Aloisi and Kevin Muscat at Melbourne Victory. Having spent most of his time in the A-League as a winger, a show of faith and position change to a central role under Fowler has been notable.

Daniel De Silva's potential has been talked about for years. Can Alen Stajcic finally help him realise it at the Mariners? Photo by Ashley Feder/Getty Images

Last season: 10th

Key additions: Daniel De Silva (Sydney FC), Kim Eun-Sun (Without club), Mark Birighitti (Melbourne City), Ziggy Gordon (Hamilton Academic)

Key losses: Tom Hiariej (FC Emmen), Jonathan Aspropotamitis (Western United), Matthew Millar (Newcastle Jets)

At a glance: In recent years, Central Coast have been playing Hinkieball without the guarantee of draft picks. Having claimed bottom spot in three of the past four seasons, Paul Okon's departure underlined an impossibly toxic environment. Samuel Silvera and Mark Moric could markedly improve via a healthy distribution of minutes from Alen Stajcic.

With a natural order in the competition working against them, a change in tact is required. However, if the likes of Michael McGlinchey, Matt Simon and Tommy Oar remain prominent in a tactical sense, more aggressive losing could be on the horizon.

Player to watch: Daniel De Silva. Insane to think he is still only 22. Not the fastest or strongest but one of the best players in the A-League in confined space. Worth watching for his first touch alone. Getting the best out of him, however, is a matter of collective deployment and integration.

Josh Brillante has made the switch from Sydney FC to Melbourne City. Speed Media/Icon Sportswire via Getty Images

Last season: 5th

Key additions: Craig Noone (Bolton), Adrian Luna (Veracruz), Javier Cabrera (Wanderers), Josh Brillante (Sydney FC)

Key losses: Bart Schenkeveld (Panathinaikos), Luke Brattan (Sydney FC), Riley McGree (Adelaide United)

At a glance: To this point, the biggest impact City Football Group has had on the A-League has been off the field. Despite the preseason insistence coming from Bundoora, Warren Joyce's absence does not immediately mean City will play better football. Erick Mombaerts' arrival has brought new training regimens, but early signs show they could be just as reliant on the transitional phase as previous seasons.

Connor Metcalfe, Denis Genreau and Ramy Najjarine could force their way into Mombaerts' primary plans, but others have arrived in their positions with greater expectations. Schenkeveld's departure has opened the door for a Harrison Delbridge-Curtis Good centre-back pairing, a high risk-high reward option for a critical element in a successful team.

Player to watch: Josh Brillante. A player somewhat incongruously thrown into Socceroos discussions while playing in Sydney, how the 26-year-old fares this season will speak volumes on both the individual's qualities and Melbourne City as a football entity. A fascinating part of this season, how he performs in a different environment.

Ola Toivonen has been named Melbourne Victory's new captain after a brilliant debut season at AAMI Park. Michael Dodge/Getty Images

Last season: 3rd

Key additions: Robbie Kruse (Bochum), Andrew Nabbout (Urawa Red Diamonds), Tim Hoogland (Bochum), Jakob Poulsen (Midtjylland)

Key losses: Terry Antonis (Suwon Bluewings), Kosta Barbarouses (Sydney FC), Keisuke Honda (free agent), Raul Baena (Atromitos), Carl Valeri (Retired)

At a glance: Watching Melbourne Victory shift furniture off the pitch might be just as interesting as how they play on it. Maybe even more, given former Adelaide boss Kurz was chosen as Kevin Muscat's replacement in the dugout. The German is a safe but arguably compatible choice, with the kind of football Victory played under Muscat in perspective.

Despite Nabbout's return to Melbourne, the announcement of Kruse's signing on the same day as Antonis' departure for South Korea underlined the sense it was a net loss in transaction. Still, he will be a key reference point for the collective when on the pitch. A year of transition, in more ways than one, for Victory and one the A-League's more expectant fan bases.

Player to watch: Ola Toivonen. Be it at ground level or on a screen, watching the Sweden international incorporate the collective off the ball last season was a joy. Clinical in front of goal, and now with added licence to roam from Kurz. Victory's season in attack could depend on how he and Kruse can facilitate the rest.

Steven Ugarkovic is arguably the best centre-midfielder in the A-League. Paul Kane/Getty Images

Last season: 7th

Key additions: Nick Fitzgerald (Western Sydney Wanderers), Matt Millar (Central Coast Mariners), Wes Hoolahan (West Bromwich Albion), Abdiel Arroyo (Arabe Unido)

Key losses: Ronald Vargas (KV Oostende), Daniel Georgievski (Western Sydney Wanderers), Roy O'Donovan (Brisbane Roar), Joey Champness (The Rap Game)

At a glance: A debilitating early-season run of injuries and suspension put Newcastle behind the eight-ball in the finals race last season. With Hoolahan's return from an ankle injury scheduled for new year, Newcastle could be treading water for the second season running.

Still, through the tandem of Steven Ugarkovic and Dimi Petratos, the Jets can never be ruled out of games. O'Donovan's departure for Brisbane could affect potency in transition and in phases of advanced defending, but the promotions of Patrick Langlois and Makis Petratos to the senior team could be impactful. Meanwhile, Millar's arrival from Central Coast is a compatible fit under Ernie Merrick.

Player to watch: Steven Ugarkovic. Although end product has room for improvement, he's the best centre-midfielder in the A-League. The 25-year-old gets his team up the pitch both on and off the ball in early and late phases, with no shortage of defensive work rate and energy. Critical for Newcastle.

Bruno Fornaroli's exile at Melbourne City is over, with the striker linking up with Tony Popovic at Perth Glory. Bruno Fornaroli

Last season: 1st (Grand Final runners-up)

Key additions: Bruno Fornaroli (Melbourne City), Osama Malik (Al-Batin), James Meredith (Millwall), Gregory Wuthrich (BSC Young Boys)

Key losses: Jacob Italiano (Borussia Monchengladbach), Andy Keogh (Al Qadisiyah), Jason Davidson (Ulsan Hyundai), Shane Lowry (Al-Ahli)

At a glance: Everything Perth Glory at the moment must be looked at within the prism of Tony Popovic's mentality and implementation, including streeting the regular season and sputtering through the finals last term. Despite his individual quality, Fornaroli's introduction could force the team -- one that already preferred to contain defensively -- back even further.

Kim Soo-beom and Meredith can make up for Davidson's departure. Malik playing in his more natural position under Popovic could see an improvement. A repeat of last regular season is by no means a guarantee, and the relationship between defence and attack will be different for the Glory this season.

Player to watch: Chris Ikonomidis. The tandem of Diego Castro and Fornaroli might receive more of the headlines, but Ikonomidis is arguably the team's most important attacker. If not the most important attacker, at least the most vertical. A combination of close control at speed and intelligent movement will always cause problems, and the 24-year-old has ample amounts of both.

Milos Ninkovic isn't just Sydney FC's player to watch... he's the A-League's best draw-card. Speed Media/Icon Sportswire via Getty Images

Last season: 2nd (Grand Final winner)

Key additions: Luke Brattan (Melbourne City), Kosta Barbarouses (Melbourne Victory), Alexander Baumjohann (Western Sydney), Ryan McGowan (Bradford City)

Key losses: Josh Brillante (Melbourne City), Siem de Jong (Ajax), Reza Ghoochannejhad (PEC Zwolle), Alex Brosque (Retired)

At a glance: The strongest team in the A-League on paper. Then again, in football, that doesn't mean much. Nor did it when they were bundled out by Brisbane in the FFA Cup this term. This will be the season Steve Corica gets to put his mark on Sydney, with two key presences under Graham Arnold in Brosque and Brillante leaving.

One still should know what to expect and it has remained from before Arnold took the Socceroos job, contrary to narratives on Corica being his own man tactically -- 4-2-2-2, meaning ultra-high full-backs, ultra-deep midfielders, everything going through Ninkovic if not in transition. But it's effective. How the likes of Brattan and Barbarouses integrate will be interesting.

Player to watch: Milos Ninkovic. Still the best player in the competition.

Ufuk Talay, left, and Ulises Davila, right, front a new-look Wellington Phoenix this season. Hagen Hopkins/Getty Images

Last season: 6th

Key additions: Reno Piscopo (Renate), Ulises Davila (Odisha), Matti Steinmann (Hamburg), Jaushua Sotirio (Western Sydney Wanderers), David Ball (Rotherham United)

Key losses: Sarpreet Singh (Bayern Munich), Roy Krishna (ATK), Andrew Durante (Western United), Max Burgess (Western United)

At a glance: Having completed a long apprenticeship, this recent extension from the Graham Arnold Coaching Tree looks set to implement a very similar style to Sydney of recent years. Ufuk Talay has been intent on new additions Sotirio and Ball as forwards in a 4-2-2-2, with Piscopo and Davila as two advanced midfielders.

An underappreciated aspect of late form last season, Louis Fenton will be prominent -- injury permitting. The void left by Mark Rudan and Singh is sizeable but, with the very existence of the Phoenix constantly under scrutiny, one that will need to be filled.

Player to watch: Ulises Davila. Specifically without Singh's ability to burst past players within confined space, the Mexican will need to hit the ground running. Once part of the Chelsea Loan Armada, Davila could be impactful.

Radoslaw Majewski will be tasked with pulling the strings from the Wanderers' midfield. Matt King/Getty Images

Last season: 8th

Key additions: Radoslaw Majewski (Pogon Szczecin), Alexander Meier (Free agent), Daniel Georgievski (Newcastle Jets), Daniel Lopar (St Gallen) Pirmin Schwegler (Hannover 96)

Key losses: Alexander Baumjohann (Sydney FC), Roly Bonevacia (Al-Faisaly), Oriol Riera (Fuenlabrada), Brendan Hamill (Western United)

At a glance: The kids were evidently not alright for Markus Babbel last season, with seven of the Wanderers' signings during the offseason aged 27 or older. Although the likes of Tate Russell and Jordan O'Doherty showed signs of improvement with their game time -- the latter particularly while playing out of position -- they will likely make way for Georgievski and Schwegler respectively.

Room for Kosta Grozos, Fabian Monge and Mohamed Adam will be minimal. Majewski looks likely to be the Wanderers' creative fulcrum but in a new stadium, vibrant fan support could be accompanied by tepid performances on the park. Plenty will be resting on Meier's goals.

Player to watch: Radoslaw Majewski. The Polish attacker won't be one to burst past defenders this season, but with sharp processing of positions on the pitch and comfort with both feet, he'll be worth focusing on while watching the Wanderers.

Andrew Durante, Valentino Yuel and Alessandro Diamanti are all part of the A-League's newest team, Western United. Robert Cianflone/Getty Images

Last season: N/A

Key additions: Alessandro Diamanti (Livorno), Panagiotis Kone (Udinese), Valentino Yuel (Bentleigh Greens), Sebastian Pasquali (Ajax)

At a glance: The concept of building an identity for a club in football can at times be overstated, considering how much it can fluctuate through whoever is coach. With Western United, narratives on identity and branding -- urgh -- are arguably peripheral.

What is more tangible, United have hired a capable coach, despite his one year in Wellington. Naturally, last season's exit from the Phoenix conditions views on United, especially considering Mark Rudan brought three players with him (Durante, Burgess and Filip Kurto). The question this season is how Rudan adapts to the players he has at his disposal. Mobility in midfield, in a formation that requires high pressing or deep defending, could necessitate some big decisions during the season.

Player to watch: Valentino Yuel. Could be crucial for Western United within context of Rudan's tactical implementation and the squad's age profile. Lightning quick, with tidy feet and calmness in front of goal, Yuel is a good chance to make a seamless transition from NPL to the A-League. Diamanti will be the primary reference point for the team in attack, but Yuel could be the one who gives the collective a certain balance. Both from attacking and defensive standpoints.