London - Chelsea on Friday announced that they had signed Demba Ba from Newcastle United, ending an 18-month spell at the Magpies during which he helped them to fifth spot in the English Premier League last season.The west London club said that the 27-year-old had joined on a three-and-a-half year contract for an undisclosed fee and would be eligible to play in the Blues' FA Cup third-round match against Southampton on Saturday."It feels good to be here, I'm very happy and very proud,' the France-born Senegal international was quoted as saying on chelseafc.com."It was important for me, and for Newcastle, to get my future sorted and now we can move on. Now they have the whole month to buy someone and for me as well, the sooner the better. Now I am here I just need to get settled in."When the club who won the Champions League wants you, the decision is very easy. This club is massive and that's something that helped the decision a lot. It was not a hard one."Newcastle confirmed this week that they had given permission to approach the player after meeting the £7 million asking price that triggered a release clause in his contract.Ba, who moved to Tyneside in 2011, was subsequently withdrawn from manager Alan Pardew's squad for the 2-1 Premier League loss at home to Everton on Wednesday evening that did little to ease the injury-hit northeast England club's woes.Chelsea's interim manager Rafael Benitez has made no secret of his search for extra options up front and with 16 league goals in his debut season and his current total this year at 13, Ba could provide that extra bite.Ba made his name during a prolific four-year spell with German club Hoffenheim and joined east London side West Ham United in January 2011 after a proposed move to Stoke City collapsed due to a failed medical examination.He scored seven goals in 12 games for West Ham but left to join Newcastle after the Hammers were relegated at the end of the 2010-11 season.Ba will also be eligible to play in Chelsea's league cup semi-final against Swansea but is ruled out of the Europa League as he has played in the competition for Newcastle.