[RPG] Can you cast spell while using “Polymorph” with sorcerer’s “Subtle Spell”

dnd-5emetamagicpolymorphsorcererspells

The polymorph spell description is kind of elusive about this:

The creature is limited in the actions it can perform by the nature of its new form, and it can't speak, cast Spells, or take any other action that requires hands or Speech. (5th Edition SRD, p. 169)

We were in an arena doing some gladiator fights and one of the foes, controlled by the DM, was a sorcerer.

My DM took it this way: spells don't require hands or speech while casting a Subtle Spell, so he could transform his character into a Giant Ape with polymorph, buffed with Mage Armor, and kept counter-spelling me since I was the only caster in the fight.

I think this is the wrong way to interpret the whole thing. My understanding is that the creature would not be able to cast spells, along with other listed limitations. But I am running out of proof. Here's the question: Who is wrong and why?

I searched a lot about the topic, but couldn't find anything. Was it included in an errata I could not find?

Best Answer

You are right, but for a different reason.

The relevant portion of polymorph here is actually this passage:

The target's game Statistics, including mental Ability Scores, are replaced by the Statistics of the chosen beast. It retains its alignment and personality.

Game statistics include special features (thanks CTWind for the rules citation), so a sorcerer who polymorphs no longer has the spellcasting class feature, the metamagic class feature, or the sorcery points class feature. Those have been replaced by the features of the chosen beast.