The Harlequins star was employed on the wing by his country last season but has made the No15 shirt his own ahead of Alex Goode and Ben Foden this term and his progress hasn't gone un-noticed by Halfpenny.
"He is a great player. He has been playing very well for a good period of time now," said Halfpenny.
"He has got a good attacking game, he's quick and he's agile. He is a player that can create something and one that we are going to have to watch.
"If you kick loosely to him, he could hurt you, so that is not something we want to be doing."
Halfpenny and Brown could easily have been colleagues when the British & Irish Lions headed to Hong Kong and Australia in the summer had the Englishman found his current form on the international stage 12 months earlier but instead it was the Welshman who outshone Rob Kearney and Stuart Hogg Down Under.
That tour came in the middle of a remarkable year for Halfpenny as he won a whole host of awards, including the RBS 6 Nations Player of the Tournament, BBC Wales Sports Personality of the Year, Midi Olympique Player of the Year and the HSBC Player of the Series for the Lions.
Throw in the collective triumph of a second successive Championship crown with Wales and a first Lions series win in 16 years and it is little wonder the 25-year-old looks back on 2013 with a broad smile.
But he isn't content to rest on his laurels, though, and is always setting new targets, the next of which is a vital victory at RFU HQ this weekend.
"I couldn't ever have dreamt of a year like it," added Halfpenny. "I am trying to maintain those standards that I set myself.
"As a player, you are always putting pressure on yourself to be the best player you can be. Ultimately, you are trying to do a job for your team and for the team to be successful.
"We are going to Twickenham as Six Nations champions and we are looking to defend our title. It's going to be a huge game and one that we are hugely excited about. England are going to be hurting from the last game. They are going to come out and want to really bring it to us. That is something we are going to have to be prepared for."