Hatfield is understood to be in final talks about taking another position at an undisclosed agency.
Rather than appointing a direct successor to Hatfield, Rapier has created a position that will see Felton take responsibility for the agency's new channel planning function, which will seek to position digital at its core.
Felton will develop multi-channel strategies for clients and use the agency's communication and data planning units to implement them. He will report to the strategy partner at Rapier, Bill Griffin.
Griffin said: "Ben has experience of creating strategies that pull all channels together and is a great hire for us. We saw a significant number of candidates for the role and Ben stood out from the start. He will be a fantastic catalyst as our model evolves."
In his former job, Felton was responsible for Agency.com's Ikea, Procter & Gamble, Dulux and Ladbrokes accounts as well as holding a position on the agency's management board.