Sotherton has long been hampered by injury with Ennis claiming the world heptathlon and pentathlon titles as well as European gold in her domestic rival's absence over the past two years.
Sotherton, the Olympic bronze medallist, competed just once this year and has opted to ditch the heptathlon in order to concentrate on the 400m which isn't on the multi-event programme.
British heptathlon is still in good hands with Ennis, once nicknamed ‘Tadpole' by Sotherton, now playing the role of mentor instead of mentee to Birchfield Harrier Hazel.
Hazel followed in Sotherton's footsteps by claiming Commonwealth gold last month and Ennis admits that has made her feel better about the two-time Olympian's decision.
"It is sad for me that Kelly has had to leave heptathlon behind because I enjoyed competing with her," said Ennis.
"She had a great career in heptathlon and I am sure she is really looking forward to the 400m and I'm sure she'll be very competitive at it.
"She will be able to concentrate on her sprinting and spend less time on all the other events and I would just like to wish her the best of luck with it all.
"Louise did brilliantly at the Commonwealth Games, they were my first major championships in 2006 and that obviously pushed me on to go forward and achieve what I have since then.
"Winning was great for Louise and hopefully she can build on that. It is always good fun to compete against other heptathletes and it will be good with her now."
Story courtesy of Sam Green of More than the Games