Michael Ballack is no more than a peripheral player at Chelsea and could be sold off by the Blues, according to Germany legend Lothar Matthaus.The Germany captain moved to Stamford Bridge on a free transfer from Bayern Munich in 2006, but has struggled to replicate the form he showed in the Bundesliga for the Blues.And Matthaus, who won 150 caps in a 20-year international career, believes Ballack could soon be discarded by Chelsea."At Chelsea Ballack is just present rather than right in the thick of things. He is a nominal player at the big London club - that is not an insult," Matthaus wrote in Sport Bild."The squad is packed with top stars. To establish yourself as a leading player there is hard. Ballack has not managed it."He is always in the first team. The question is only: For how much longer?"