A few things:
He's only playing because Riera's been so bad of late. Rafa prefers the latter, and for most of this season Babel's been thrid choice left-winger behind Albert and Benayoun.
Salomon Kalou and Joe Cole are better player, and they even get on for Chelsea. That's an indication of squad contrast right there.
Still, he's taken his chance well of late. I'd like to see him continue there, but only if the tactics and formation around him allow him to focus for the most part of attacking.
Long-term, we need better.