New coach Scott Johnson promised to help the Ospreys "realise their full potential" after his arrival in Wales.
"The Ospreys have been a real success story in recent years and I'm looking forward to working with the coaching team to help build on that," he said.
Johnson, who has signed a three-year deal, will initially take an observational role before fully taking over as Ospreys' director of coaching.
Head coach Sean Holley and assistant Jonathan Humphreys stay at the region.
Former Wales lock Gareth Llewellyn says Johnson can turn the Ospreys into the "formidable force they should be".
Llewellyn, capped 92 times, played under Johnson when the Australian was Wales skills coach and believes he can make an impact at the Liberty Stadium.
"I think in the long term he will make a fantastic difference," he said.
"Just speaking from experience of working under the guy, I think he's a fantastic coach and probably one of the best rugby coaches I've ever worked under.
"I think he will make the Ospreys the formidable force they should be with the players they've got at their disposal.
"He will have a view of what the Ospreys have got in terms of player resource and he will build a game plan that will suit it."
Johnson was handed the job in January, but had to serve three months notice as coach of USA before returning to Wales.
The Australian was skills coach with Wales under Steve Hansen and Mike Ruddock, before leading Wales in three internationals in a caretaker role after Ruddock's shock departure in 2006.
He left to become Australia attack coach, but departed after their poor World Cup showing in 2007.
Johnson remains close friends with Cardiff Blues director of rugby Dai Young, leading to speculation last year that the Australian could take up a coaching role at the Arms Park.
Instead he opted to move to North America to take the Eagles head job last year.
SCOTT JOHNSON CAREER
Born: Sydney, 19-08-62
Player: Fly-half/centre, NSW & Australia U21
2001: Named Australia A assistant coach and NSW Waratahs assistant coach
2001-6: Wales skills coach
2006: Wales caretaker coach
2006-7: Australia attack coach
2008-9: USA Eagles coach
2009-: Ospreys director of coaching
Holley had wanted the director of coaching role himself, but Llewellyn says he only has himself to blame for missing out.
"I think Andrew Hore came out at the start of the season and said their possible long-term coach may be Sean Holley," Llewellyn told BBC Wales' Scrum V Radio programme.
"The opportunity was there for them [Holley and Humphreys] to set their stall out, really get the Ospreys operating and performing well, but they haven't.
"And it's not a one-off game where the Ospreys haven't performed... it's every time you watch them.
"I very rarely come away from watching the Ospreys without feeling depressed and unfulfilled at the amount of potential that's there yet we're not seeing it on the field.
"You never get the sense that it's the team ethic and the team principles that's winning the game."
Johnson said he was thrilled to be returning to Wales.
"[It's] going to be something of a homecoming for me and I can't wait to work again with players and coaches I know well from my time with the Welsh team, as well as the exciting young talent that is coming through," he said.
"Refining the team's rugby performance and development programme is going to be a career defining experience for me.
"This is a perfect opportunity to help develop and enhance the Ospreys' pitch presence and game-play.
"It's a task that means working on different levels throughout the organisation, helping deliver a stream of subtle improvements combined with innovation that, when taken together, can make a big impact."
We have underachieved and failed to live up to our potential. Scott's arrival is extremely timely
Ospreys boss Mike Cuddy
Ospreys managing director Mike Cuddy added: "[Johnson] brings with him a reputation as an exciting, innovative and visionary rugby brain, who we're sure will hit the ground running.
"The search for a director of coaching has been a lengthy one, but we're in no doubt that in Scott we have found an individual with the qualities we need to see us make a giant stride forward on the pitch.
"It has long been our stated desire to see the Ospreys firmly established amongst the leading sides in European rugby, a goal Scott shares with us.
"He has a passion for Wales, and for Welsh rugby, and has vast knowledge not only of domestic rugby but wide ranging international experience at the very top level.
"Our recent performance has been extremely disappointing, we have underachieved and failed to live up to our potential. Scott's arrival is extremely timely.
"We had previously identified where the organisation needed to be strengthened and his appointment is a part of a much wider plan aimed at re-establishing and enhancing the Ospreys' on-pitch performance."
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