Manchester City completed their shock swoop for Owen Hargreaves on Wednesday as the injury-plagued former Manchester United midfielder signed a one-year contract with the Premier League club.
Hargreaves was released by United at the end of last season after the champions rejected his offer to play for free following a miserable four-year spell at Old Trafford.
The former England star suffered a series of knee injuries following his move to United from Bayern Munich in 2007 and spent much of the close-season trying to convince potential employers that he was still capable of playing at the highest level.
City believe Hargreaves is completely recovered from his knee surgeries and they put the finishing touches to the deal after the 30-year-old passed an extensive medical over the last 24 hours.
"Owen Hargreaves has become the latest of Roberto Mancini's summer signings," a statement on City's website confirmed.
"The England midfielder joins as a free agent having left Manchester United at the end of last season. He has put pen to paper on a one-year contract and will train on Thursday."
Hargreaves, who also had an offer on the table from West Brom, has hardly played since being forced to undergo operations on both knees to cure a debilitating tendinitis problem.
He lasted just five minutes of his only Premier League game last season, against Wolves at Old Trafford in November, when he tore his hamstring and he then dislocated his shoulder and was unable to return to fitness before the end of United's title-winning campaign.
The Calgary-born player recently described the injury against Wolves as the lowest moment of his injury nightmare, but he had no intention of quitting and posted videos of his training regime on YouTube in a bid to win a return to football.
Prior to his injury problems, Hargreaves had been an England regular, winning 42 caps, and was regarded as one of his country's stand-out performers at the 2006 World Cup.
He played in Manchester United's 2008 Champions League final victory over Chelsea, having already become only the second English player to win the competition at a foreign club with Bayern.
Hargreaves' arrival on transfer deadline day should complete Mancini's extensive close-season revamp of City's squad.
He becomes the Italian's sixth signing and could face an emotional reunion with Bayern when City take on the German club in the Champions League at the Allianz Arena on September 27.
If Hargreaves can win a place in Mancini's midfield ahead of the likes of Gareth Barry and Nigel de Jong, he will have a chance to prove Wayne Rooney wrong when City travel to United on October 23.
Rooney this week admitted he was uncertain if Hargreaves could ever recapture his old form after so many injury problems.
"He got back last season, played one game, and then did his hamstring. It will be difficult for him to get back to his best but I hope he can," Rooney said,
"He's been out for a couple of years now and, to be fair to him, he's worked really hard. If he can get back, great, but it is going to be difficult for him."