Inter made several tactical experiments, but needed a Giampaolo Pazzini brace to fight back from 2-0 down against 10-man Olympiacos.
Gian Piero Gasperini prepared for life after Samuel Eto'o and continued his tactical experiments in Geneva, as the team moved from 3-4-3 to 4-3-2-1 at various points during the friendly.
The first switch to four at the back came after just five minutes. Luc Castaignos had a shot charged down by the goalkeeper, but Olympiacos went down to 10 men before the half-hour mark for Mellberg's second bookable offence.
Inter returned to 3-4-3 and went close when Thiago Motta, Diego Milito and Ricky Alvarez combined, but the latter scuffed his finish.
There was a surprise straight after the break, as 10-man Olympiacos took the lead with Feisa nodding in from a free kick at the near post.
Goran Pandev thought he had equalised on an Esteban Cambiasso assist, but it was ruled offside.
The Greek outfit went 2-0 up through Modesto, who pounced on Andrea Ranocchia's poor clearance with a daisy-cutter, completely undisturbed on the edge of the box.
Substitute Giampaolo Pazzini managed to get one back for the Nerazzurri by tapping in a smart Marco Faraoni through ball.
Pazzini made a huge impact on the game and completed his brace as well as Inter's comeback with an acrobatic finish to knock the corner over the line.
Olympiacos 2-2 Inter
Scorers: Feisa 47 (O), Modesto 68 (O), Pazzini 76, 89 (I)
Sent off: Mellberg 27 (O)
Olympiacos: Costanzo; Modesto, Papadopoulos (Papazoglu 56), Mellberg, Marcano; Feisa (Potouridis 76), Hurtado; Fuster (Maniatis 46), Yeste (Holebas 56), Fetfatzidis (Javito 56); Mirallas (Pantelic 63)
Inter: Julio Cesar; Zanetti, Samuel (Ranocchia 51), Chivu (Faraoni 74); Jonathan (Pandev 46), Thiago Motta, Cambiasso (Crisetig 91), Obi; Alvarez (Pazzini 46), Milito, Castaignos (Santon 64)