Argentine striker Franco Di Santo signed for Premier League heavyweights Chelsea from AudaxItaliano in the Chilean league. Chelsea paid around £3.4m to sign him as a teenager officially during the 2008 winter transfer window.

Franco Di Santo started his Chelsea career on a good note scoring for the reserves on his debut. He scored a late goal as Chelsea reserves and Fulham reserves played out a 2-2 draw on February 11, 2008.Di Santo scored his second goal for the Chelsea reserves against Reading reserves on March 3, 2008. His goal against the Reading reserves made it two goals in two games for Chelsea reserves.

On April 14, 2008, Franco Di Santo scored his first treble for the Chelsea reserves in the London Derby clash with Tottenham Hotspur reserves. The final goal of the hat-trick was the best as he volleyed home a cross from Serbian defender BranislavIvanovic. In the final match of the season for the Chelsea reserves, Franco Di Santo scored against Aston Villa reserves thus making it seven goals in his last eight matches for the Chelsea reserves. He finished the season with an impressive record of 12 goals for the Chelsea reserves despite the fact that he signed for the club in the middle of the season.

At the start of the 2008/09 season, Franco Di Santo trainer with the Chelsea first team during pre-season and he flew out with the team on their China tour. Di Santo was given the number 36 jersey on the tour of China and he came on as a second half substitute against local team Guangzhou Pharmaceutical to score the third goal in a 4-0 win. He scored again five minutes after coming on as a substitute for Frenchman Nicholas Anelka in the 7-0 rout of Chengdu Blades.

Franco Di Santo played his first competitive game for the Blues in the 1-1 draw with Tottenham Hotspur in the London Derby in the league having come on as an 88th minute substitute.