Adelaide United goalkeeper Joe Gauci has signed for English Premier League bolters Aston Villa, joining the mass exodus of players to leave the A-League club this season.

Aston Villa has completed a deal to sign the up-and-coming goalkeeper until 2028, for an undisclosed transfer fee that is reportedly in the millions of dollars.

The 23-year-old, who is currently with Australia's squad competing at the Asian Cup, has completed a medical and will link up with the club after the tournament.

Speaking on the move, Gauci thanked Adelaide United and its fans for the support he had received over the past three-and-a-half seasons.

"The love you've given me over this period has made these memories even more memorable and they are something I'm going to carry with me for the rest of my life," he said.

"I would also like to thank all the staff members and players, past and present, that have supported me through this journey.

"The environment the club has created has really allowed me to flourish and be my true self, on and off the field, that has allowed me to reach the level that I have."

The South Australian has been Adelaide's number one goalkeeper for the past two seasons, grabbing the position ahead of former starter James Delianov, who suffered a shoulder injury at the start of 2022.

He will likely be a depth option in goals at Villa, given the club’s first-choice gloveman Emiliano Martinez is a World Cup winner with Argentina.

Adelaide United coach Carl Veart said it is a dream move for Gauci.

"I don't think it [could] be any better for Joe," Veart said.

"He's shown to all our young players at our club, if you're prepared to do the right things and work hard and focus on getting the best out of yourself, the rewards will come."

While Gauci is reaping the rewards, Veart is left to pick up the pieces, having lost six players to transfers this season alone.

Craig Goodwin joined Saudi Pro League side Al-Wehda, and Nestory Irankunda will make a big-money move to German powerhouse Bayern Munich at the end of the season.

Goalkeeper Steven Hall also left this month, signing for Premier League side Brighton and Hove Albion.

Winger Bernardo, who is the son of club legend Cassio, left to join Macarthur FC earlier this month, and this week defender Alexander Popovic also exited, joining K League 1 side Gwangju FC.

Forward Musa Toure has also been linked with Scottish Premier League side Hibernian FC.

Former skipper makes return

The club has made a move to address its lack of depth, announcing former skipper Stefan Mauk has rejoined the club.

The experienced midfielder has been training with Adelaide for the past few weeks since returning to Australia from Asia, and re-joins the club from J2 League club Fagiano Okayama.

Mauk has scored 13 goals in 63 appearances for the club, with his long-term deal keeping him at the club until the end of the 2026/27 season.

"Adelaide has always held a special place in my heart, and I am genuinely excited to be back," he said.

"Returning to Adelaide United feels like coming home — the camaraderie among the players is truly special."

Veart said it is an addition his squad desperately needed.

"We're very happy, not just with the calibre of Stefan on the pitch, but off the pitch, his leadership, so it's going to be a great boost to the squad," Veart said.

"We've been patient with Stefan to give him that opportunity, he still had aspirations to stay in Asia.

"At this point in time we had to make a stance. He needed to make a commitment to us and he has."

While Mauk has come in, United still needs more reinforcements.

Veart said the club is in discussions with "two to three other players", but he admitted it can be difficult to attract players to Adelaide with the club's budget.

That is despite the club making big profits from recent sales of Goodwin and Irankunda.

Goodwin's move to Al-Wehda reportedly netted the club close to $1 million, while Irankunda's blockbuster fee is understood to be about $5.5 million.

Gauci's sale to Aston Villa is also reportedly worth $2.5 million.

"It's not about not being able to bring players in, it's about finding the right players that will come in and fit in with our style of play and the culture we've got in the dressing room," he said.

"But we've got people looking and working extremely hard on it and at the moment we're still trying to find a couple more players to bring in."

Proud to be a development club

Despite having to manage an ever-changing squad, Veart said he was proud to be a part of a club that focuses on player development.

Veart is known for giving young players more opportunities than they may get at other clubs around the league, and his coaching has led to increased opportunities for players abroad.

Awer Mabil joined Danish club Midtjylland after a stint with the Reds, and Mohamed Toure, Yaya Dukuly and Socceroos pair Riley McGree and Mathew Leckie also moved overseas from the club.

Veart said the club's philosophy would remain the same.

"They all start at junior clubs, so, it's something that we've done quite well over the last three or four years.

"It's something that we're going to keep pushing, it's important that we provide that platform for young players to use the club as an opportunity to reach their dreams."

Adelaide is currently in eighth position on the A-League ladder, with five wins from 14 games so far this season.