The former England back-row forward has started work at Sixways in preparation for next season. Worcester finished 11th in the Premiership this term, losing their final game to bottom club London Welsh three days ago.
It represented another disappointing campaign for the Warriors, and Ryan, who knows there is a lot of work to be done, said: "I am excited to be back in the game. I am excited to be with Worcester Warriors Rugby Club, and I am looking forward to what is a huge challenge."
The former Gloucester rugby director, who has been working as a television rugby pundit and also assisted Scotland in a coaching capacity during their 6 Nations campaign this season, added: "Right from the outset to come back into rugby was about finding something that did excite me.
"In my own head I got to a place where I thought I was going to carry on with TV. I didn't really see a challenge that lit the fire back inside, and I think conversations with Cecil (Worcester chairman Cecil Duckworth) is something that started to do that.
"The opportunity here to restructure how the club goes forward was almost a challenge that, if I didn't do it, would eat me away further down the line."
Worcester won just five league games this term, and lifting them away from the Premiership's lower reaches will be Ryan's priority next season.
"I don't think there is a simple answer, otherwise it would have been found before, and it would be nave to think there is," he added. "It is about breaking a cycle of operating in that bottom three or four clubs.
"I am not naive enough to throw things around and think I'm going to come in here with a magic wand.
"We've got to restructure the club so that as it goes forward over the years it starts to get the benefits of certain things that have been put in place."
- Sports & Recreation