I think that obviously no other group in italy can really take on the local mafia groups, same could be said for foreign groups if they are in nigeria.
But you cant really call Nigerians small time, they practically invented the 419 scam and also involved heavily in drug trafficking, including importing and distributing heroin in the USA. Actually i think they have been mentioned more frequently in the US drug threat assessment reports than italian OC, which i think have only been mentioned once in the past few years.