Catania lost their high-profile friendly against Real Sociedad 2-1, falling to a late goal.
Vincenzo Montella could not count on new signing David Suazo yet at the Stadio Massimino.
Illara's header from point-blank range was well beaten away by the goalkeeper, but Real Sociedad did get their opener when Nicolas Spolli accidentally scuffed a harmless cross into his own net.
Catellani fired straight at the Spanish ‘keeper and moments later Alessandro Potenza got his head to an Alejandro Gomez free kick for the equaliser.
Adrian Ricchiuti's screamer was tipped out from under the crossbar in the second half and Maxi Lopez forced another save in what could well be his last appearance in a Catania jersey.
However, Real Sociedad won the game 2-1 in the final minutes with a fierce Sarpong strike.
Catania 1-2 Real Sociedad
Scorers: Spolli og 31 (R), Potenza 38 (C), Sarpong 81 (R)
Catania: Campagnolo; Alvarez (Marchese 75), Potenza, Spolli (Augustyn 80), Capuano (Bellusci 55); Ledesma (Ricchiuti 62), Lodi (Sciacca 75), Moretti (Izco 27); Barrientos (Lanzafame 46), Catellani (Maxi Lopez 67), Gomez (Keko 80)
Real Sociedad: Bravo, Martinez, Demidov, Ingo Martinez, De La Bella, Elustondo, Illarra, Ruben Pardo, Prieto, Ifran, Sarpong
Tickets for the Champions League final between Juventus and Real Madrid are still on sale with reseller Viagogo - Click to find out more