i reckon it would be possible with barca...
i know that technically it doesn't count as obviously my team is far better then the opposition but using an upside down leagues edit i've made my way up to league 2 as manchester united and am at the end of janurary with the last time my team failed to win being my last friendly before the start of the season. the run so far is including a 2-1 league win over city and cup wins against chelsea and liverpool.