Leaders Inter prevailed 2-0 to go two points clear of Roma in the Serie A title race, but the game was overshadowed by Lazio fans cheering the goals against them given their bitter city rivals slipped off top spot.
Lazio, still not mathematically clear of relegation with two games left, pushed Inter in the first half but once they conceded the match petered out as a contest.
"After what we have seen, to call our championship the most beautiful in the world is absurd. If I was Inter I would be ashamed of winning like that," Roma president Rosella Sensi told reporters.
The final at Rome's Stadio Olimpico was already shaping up to be an epic duel without the added spice.
The final is now a one-off game, pre-planned in Roma's stadium, with both teams taking it much more seriously than they usually would for the much-maligned Italian Cup.
"It will be hard in the Cup on Wednesday because Roma are on form and they aren't giving up, but we will give everything to win the first trophy available to us," Inter's former Roma defender Walter Samuel said.
