When mages don't cast...

[Einthoven]

I had a surprising thing happen in a recent game - I had ordered a mage with Level 3 in a path to cast a level 3 battlef ield spell (which requires a magic gem) at the beginning of his combat orders.

Watching the replay, the mage doesn't cast the spell but rather a defensive spell, then for his 2nd through 5th spells are as I ordered them. Now the mage seems to have all the right levels to cast the spell (it isn't greyed out in his spells list), and he does have the right number of gems, so I'm trying to figure out why he didn't cast the spell.

He's not feebleminded or afflicted with any wounded states, so any thoughts on what I did wrong?