Allen's new club Liverpool host the Swans in the Capital One Cup and Monk says there will be no ill-feeling towards the Welsh midfielder who left the Liberty Stadium for Anfield in the summer.
"He is a top player. Everyone knows his quality as a player, and he is a great lad too," Monk said.
"A few of us have had a bit of banter with him, winding each other up. But it will be great to see him, I am really glad to see he is doing so well.
"He is a great lad and a great talent and he is proving it now at a very high level."