Capello wants Beckham to be part of the squad as a non-playing member.
Murphy, who was forced to withdraw from England's 2002 World Cup squad after breaking a metatarsal, said: "I think Beckham being there would detract from the main event. The focus needs to remain on what is important.
"Even though he has great experience and he would help, I think the media element alone would be very difficult to manage."
Fulham midfielder Murphy knows all about the attention that follows Beckham around after being involved in the build-up to the 2002 tournament in Japan, when Beckham-mania was at fever pitch.
Murphy added: "I think Becks can take comfort from the fact that he has gone to three World Cups already and been fantastic, so he has those memories.
"He has been brilliant. However, I think taking David to the World Cup as part of the staff would be wrong.
"He is a player so once he is out of it through injury he should stay out and the other guys need to regroup and move on."