Not his job. Mourinho wasn't using him as a destroyer - Sami Khedira, and, to a lesser extent, Xabi Alonso's positioning were his lines of defence - he was playing an unfamiliar role as a passer rather than a runner. As Subtle pointed out, he played it pretty **** well, with a higher pass accuracy than anyone for City, and a couple of key passes into the bargain. He admittedly fell off in the second half, after I said that he was running the midfield, but considering this is his first Champions League match in a while and he's short of fitness as it was an admirable performance.