On 18 May 2008, after Siena's 2–2 draw against Palermo in the final matchday, Beretta said in his press conference that he was quitting Siena. This was confirmed by the club a few days later; he left Siena after a very impressive season ended with a record 44 points, the best result in "Robur"'s time in the Italian top flight. He was successively announced on 23 June as new head coach of Lecce, newly promoted in the 2008–09 Serie A. He was sacked on 9 March after a 0–0 home draw against bottom-placed Reggina in the Week 27 of Serie A that left Lecce in second-last place.