Woah, didn't notice that. I assume he did it really quick. At first it was himself, then after Aizen made his move in about 0.000000000000000000001 of a sec, he inflated his Gigai, let it take the hit, placed the seal on his wrist and Shunpo behind Aizen for the Bakudan move(s).
Duuuuh.

But yeah, that's really stupid. Is it the same in the manga?