Chelsea have signed Argentinian teenager Franco Di Santo on a four-and-a-half-year contract.The Barclays Premier League club have made no mention of a fee for the Argentina Under-20 international striker. He joins the Blues from Audax Italiano in Chile. The 6ft 4ins striker has incredibly been compared to diminutive legend Diego Maradona. Chelsea had been reported to have agreed a deal worth more than £3million for Di Santo, who holds an Italian passport. Chelsea reportedly saw off competition from the likes of Manchester United and Liverpool to sign the tall frontman.