Most glaring mistake was a silly handball that led to a penalty (which luckily, Hernanes missed in hilarious fashion). Made other mistakes as well, overall not a good game from him. But he's had many many good games this season and like you said, he's still young so I definitely wouldn't give up on him. Perhaps still needs 1-2 more years to develop.
I did say in Which CB would you sign? thread, that it's a pity that he's not a couple years older and he would've eliminated these errors from his game. Hopefully this will happen in this next few years, while running his contract down in order to secure a cheap move to Barca .
So Inter currently only have one senior striker left in the side - Grandpa Rocchi. Milito, Palacio, now Cassano all out with long term injuries. Have a feeling it's going to be a cringeworthy rest of the season, unless some kid really really steps up.