Clearly, an outboard engine failure is more critical than a center engine failure because it causes asymmetric thrust in addition to reduced thrust, and thus requires gimballing or reduction of the engine opposite it, with further reduced thrust as consequence. CRS-1 used a Falcon 9.0 booster with engines placed in a 3×3 orthogonal grid (rather than today's octaweb) which means that a corner engine failure would cause even more severe asymmetry than a side engine failure.
It is therefore interesting to know the position of the failed engine. Which engine was "engine 1"?
For reference, the orthogonal 3×3 grid of Falcon 9.0 vs. the octaweb of later versions: