Former Manchester United star Ruud van Nistelrooy has announced his retirement after not renewing his contract with La Liga side Malaga.The former Netherlands international's contract is due to expire at the end of the season, bringing down the curtain on a glittering 20-year career that has included stints with United, PSV, Real Madrid and Hamburg."Yesterday I played the last match of my professional career," Van Nistelrooy told a packed press conference."The time has come to hang up my boots. I want to thank all the clubs I've played for over the years for their support."I want to thank my friends and family, who have supported me all these years. I also like to thank the fans of all my clubs - they have been great."The 35-year-old started his professional career with Dutch Eerstedivisie side Den Bosch in 1993 before joining Heerenveen four years later.He then made the move to Dutch giants PSV, prompting his selection in the Dutch national team, and eventually earned a big-money transfer to Manchester United in 2000.Van Nistelrooy was a key figure at Old Trafford netting 150 goals in 219 appearances before joining Real Madrid in 2006, where he won two La Liga titles.Well known for his sharp movement in the box and ability to poach goals, the Dutchman went on to spend 18 months at Hamburg, before joining Malaga at the start of the 2011-12 season.Van Nistelrooy made 70 international appearances for Netherlands scoring 35 goals, and is still the Champions League's second highest scorer with 56 goals.