Great Britain will not risk in-form Marlon Devonish in the 200m at next month's World Championships in Osaka.
Devonish won both the 100m and 200m at the trials in Manchester
The 31-year-old sprinter has been picked for the 100m but selectors want to keep him fresh for the relay.
World marathon record-holder Paula Radcliffe has been left out of the team as she recovers from a back injury.
Triple jumper Phillips Idowu has been included despite fitness concerns, while 400m runner Christine Ohuruogu could return after a 12-month ban.
Devonish is disappointed not to be doubling up after winning both sprints at the trials in Manchester but feels it is the right decision to miss the 200m.
"Looking back, the focus has been on individual events for me, but things have changed," he told BBC Five Live.
"We are now working towards the relay a lot more and it's become quite a fundamental part of the whole set-up.
"In an ideal world what I'd love to do is run the 100m, see what happens in the 200m and then do the relay."
We are not stopping anyone doubling up, we are just a bit worried about them tripling up
UK Athletics performance director Dave Collins
Explaining the decision not to risk Devonish in the 200m, UK Athletics performance director Dave Collins said the Coventry Godiva star's best chance of an individual medal was in the 100m.
"This year he's done fantastically well in both, but he's looking a genuine final probability in the 100m," said Collins.
"We are not stopping anyone doubling up, we are just a bit worried about them tripling up. The relay is an important medal opportunity, arguably our best medal opportunity."
Ohuruogu, whose suspension expires on Monday, could also force her way into the team in the 400m relay squad.
The 23-year-old, who already holds the qualifying time from last season, was banned for missing three out-of-competition drugs tests, but she is taking part in a special time trial at Crystal Palace on Thursday.
A UK Athletics spokesman said selectors would take account of Ohuruogu's performance in that run, which has been set up by her coach Lloyd Cowan, when choosing the team for Osaka.
Ohuruogu is believed to have been performing well in training, and an impressive performance in the trial - which will not be a competitive race - could see her welcomed back to the fold.
Despite missing out on the Worlds, Radcliffe, who had a baby in January, has confirmed her intention to return to action in the autumn.
"I'm not going to rush or take any short-cuts trying to get back competing," said the Bedford star, the only Briton to win an individual medal at the World Championships in Helsinki two years ago with a storming marathon performance.
"If things go to plan, I am hoping to return to racing in the early autumn."
The 33-year-old was back into training soon after her daughter's arrival but suffered setbacks as stress fractures at the bottom of her spine, linked to childbirth, and they stemmed her enthusiasm for competitive action.
Radcliffe was the only Briton to win an individual medal at the World Championships two years ago
"I've only done a couple of track sessions and I bruised my foot in one," she added.
"I had to back off and there's no way I'm going to set off my back problem again by being impetuous."
The 49 athletes already picked are described as "first wave" selections with a second and final list of athletes to follow on 7 August.
That second wave could yet include sprinter Mark Lewis-Francis, who finished third at the UK Championships at the weekend.
Meanwhile, the selectors have left places open for 400m athlete Tim Benjamin and 800m runner Becky Lyne.
Benjamin and Lyne have struggled with injury in recent weeks, but both will run in the London Grand Prix on Friday.
Idowu, one of Britain's few genuine medal contenders, pulled out of the UK Championships at the weekend after just one jump and has made it clear that he will not travel unless he is fully fit.
I'm satisfied the selection panel has picked a team capable of supporting our ambitious targets for Osaka
Fellow triple jumper Nathan Douglas is definitely out because of a serious hamstring injury.
As well as Douglas, Sam Ellis and Rhys Williams - European bronze medallists in the 800m and 400m hurdles respectively - will miss the trip to Japan because of injury.
"I'm satisfied the selection panel has picked a team capable of supporting our ambitious targets for Osaka," said Collins.
"The team is full of talent and we will be looking for every member of the squad to step up and perform to the high level required at a World Championships."
UKA have stated that their target for Osaka is to get 14 athletes to reach their respective individual finals, with 20-25% of the finalists going on to win medals.
The World Championships begin on 25 August in Japan.
Great Britain team for World Championships (First Wave Selection):
100m: Marlon Devonish, Craig Pickering
400m: Martyn Rooney, Andrew Steele
800m: Michael Rimmer
1500m: Andy Baddeley
5000m: Mo Farah
Marathon & IAAF World Cup: Peter Riley, Daniel Robinson
3000m steeplechase: Andrew Lemoncello
110m hurdles: Andy Turner
400m hurdles: Dale Garland
High Jump: Martyn Bernard, Germaine Mason
Pole Vault: Steve Lewis
Long Jump: Greg Rutherford, Chris Tomlinson
Triple Jump: Phillips Idowu
4x100m relay: Marlon Devonish, Tyrone Edgar, Mark Lewis-Francis, Craig Pickering
4x400m relay: Tim Benjamin, Martyn Rooney, Andrew Steele, Robert Tobin
100m: Montel Douglas
200m: Joice Maduaka
400m: Nicola Sanders
800m: Jemma Simpson, Marilyn Okoro
1500m: Abby Westley, Lisa Dobriskey
5000m: Jo Pavey
10,000m: Jo Pavey
Marathon & IAAF World Cup: Tracey Morris, Mara Yamauchi
3000m steeplechase: Helen Clitheroe, Hatti Dean
400m hurdles: Tasha Danvers-Smith
Pole Vault: Kate Dennison
Javelin: Goldie Sayers
Heptathlon: Jessica Ennis, Kelly Sotherton
20km walk: Joanna Jackson
4x100m relay: Montel Douglas, Emily Freeman, Jeanette Kwakye, Joice Maduaka, Laura Turner
4x400m relay: Vicky Barr, Donna Fraser, Lee McConnell, Jenny Meadows, Nicola Sanders