Rio Ferdinand is leaving Manchester United after 12 years, with the club having decided against offering him a new contract. The defender's departure was confirmed on the day United had a £27m bid for Southampton's Luke Shaw rejected, signalling that a summer of rebuilding has begun in earnest.

Ferdinand said recently that he hoped to stay at United and he is determined to continue his career. The former England captain and centre-half, at 35, is keen to play on in the Premier League if he receives an offer that suits. He will weigh his options carefully and is sure to field offers from abroad, including from Dubai, China and Major League Soccer.

There is the strong possibility that Ferdinand will move into coaching at some point, so a player-coach role may be considered. Ferdinand, who is from Peckham in south London, had been away from his home town since being transferred from West Ham United to Leeds United in 2000.

Harry Redknapp, who gave him his first-team debut at West Ham, is now in charge of Queens Park Rangers. The pair continue to enjoy good relations and Redknapp may try to tempt him to join the club as a player and as part of his backroom staff.

Ferdinand's departure ends a highly successful spell at United where, having being signed from Leeds United in July 2002 for £30m, a record for a defender, he won six Premier League titles, the Champions League and two League Cups.

In a statement on his website Ferdinand implied that the decision to leave Old Trafford was his, although it is understood this was not the case. He has not been a regular first-choice this season and has been troubled by injury.

"I have thought long and hard over the last few months about my future and after 12 fantastic years playing for what I regard as the best club in the world I have decided the time is right for me to move on," he said.

"I joined Manchester United in the hope of winning trophies and never in my wildest dreams could I have imagined how successful we would be during my time here.

"There have been so many highlights, playing alongside some great players who have become good friends, winning my first Premier League title and also that fantastic night in Moscow are memories that I will cherish forever.

He added: "Circumstances didn't allow for me to say goodbye the way I would have liked but I'd like to take this opportunity to thank my team-mates, staff, the club and the fans for an unbelievable 12 years that I'll never forget.

"Winning trophies I dreamed about as a kid came true at this great club. I am feeling fit and healthy, ready for a new challenge and looking forward to whatever the future holds for me."

United tweeted: "#mufc would like to thank Rio Ferdinand for his long and distinguished service, and wish him well for the future."

As the club plan for their own future, they have been told by Southampton that Shaw is not for sale but United are still confident of securing the left-back's transfer, with Southampton's stance viewed as a bargaining position.

United value Shaw in the region of £30m, with the 18-year-old, who was named by Roy Hodgson in England's World Cup squad on Monday, keen on the move.

His preference is that the deal should be completed before the tournament begins in Brazil next month. United believe they can conclude the transfer that would make Shaw the most expensive teenager in domestic football history and the best rewarded.

As reported by the Guardian, United will make Shaw the highest-paid player ever under 20 by offering him a £100,000-a-week salary over five years and are set to beat off interest from Chelsea and Manchester City for his signature.

These terms would quadruple his earnings and would see Shaw placed well above the bracket of Adnan Januzaj, who when agreeing a fresh five-year contract at Old Trafford last autumn accepted a salary of around £60,000 a week.

United finished seventh in the Premier League following a dismal title defence and are expected to appoint Louis van Gaal as their manager this week. Although the club do not plan to have a formal unveiling of the Holland coach until after the World Cup, Van Gaal will have been consulted over Shaw to ensure the Dutchman would want him.

There are doubts over whether two of the coaching staff, Phil Neville and the goalkeeping specialist Chris Woods, will be kept on.

Shaw would represent the first signing of what United hope will be a major overhaul of the squad in the summer transfer window. Yet despite the club being in a state of flux until a new manager arrives – Ryan Giggs's interim tenure ended on Sunday – Darren Fletcher has claimed this should not concern players too much.

"I think you can sometimes worry too much about that," the midfielder said. "It's important to focus on yourself and make sure you come back for the new season in the right condition and whoever is the manager you have to try to impress him in pre-season and training. It's never been any different here and that's always been my mindset. It's a big squad with competition for places and you have to impress when you get an opportunity."