Why couldn't Eren Yeager transform into a Titan in the last episode of season 2?


In the last episode of season 2, named "Scream", Eren Yeager was unable to
transform into a Titan to save Hannes from the Smiling Titan.

Why couldn't he transform?

I don't really read the manga, although I do look at it from time to time.

Has there already been an explanation for this in the manga?




According to the [Power of the
Titans](http://attackontitan.wikia.com/wiki/Power_of_the_Titans) wiki (
**disclamer, this page contains heavy spoilers from the manga)** , the ability
to transform into a titan may be hindered if an injury occurred after a recent
transformation.

> The ability to transform into a Titan can be hindered by injuries inflicted
> on the human body. A human can transform into a Titan with injuries as
> severe as a missing limb, but only if a previous transformation has not
> occurred recently. **If a human emerges from their Titan form and receives
> severe injury, this person cannot transform into a Titan again until said
> injuries have healed**

In the episodes leading up to this event

> We see Eren face off with the Armored Titan, but ends up being captured
> along with Ymir. They soon awaken with their arms severed off to prevent
> from the escaping.

and in [S2, E9](http://attackontitan.wikia.com/wiki/Opening_\(Episode\))

> _Reiner informs the two that neither of them could transform into Titans in
> the first place while still recovering from their injuries_

When Eren attempted to transform in the final episode, his body was still
recovering from this injury inflicted on him.

