What is Harting's "ace up his sleeve"?

i think most of you have read the article with Harting about his 2015 Off-Season Training?

Here it is:
2015 Off-Season Training With: Robert Harting | Throwholics

He is talking in the end about "an ace up his sleeve".
What do you think will it be?

If your answer option is not given, just add it

I just added the possibility to add own answers as well.

Quote from Tabór Abarca

Does he not have a new coach in the past year?

Yes he switched to Thorsten Schmidt.

Quote from Tabór Abarca

There might be many changes.

Lets just think of what CHristoph did last weekend....

You are talking about Christoph Harting, aren't you?

The first post and poll was about the older brother Robert.
But you are right, the technique of Christoph has changed a lot and I think improved.