Assuming Akainu is the fleet admiral still... It's unlikely Akainu would throw away an asset like Doflamingo off just killing Smoker alone. So I can see Doflamingo testing his luck here and getting some burns as a result.
If he's rogue? Doffy doesn't get the opportunity to know Akainu is there, he's burned badly and Akainu's coming at him for blood.