The Northern Irishman is certainly making a big impression - not least on compatriot O'Neill, who was unaware of McClean's talents before arriving at the club.
"He is performing brilliantly for us," O'Neill said.
"He has had a great, great couple of months. Considering everything, I thought he took his goal brilliantly.
"I didn't know him at all until I arrived at the football club, so to see him blossoming out there has been very pleasing for everyone, obviously myself included."