Craig Pickering believes Marlon Devonish should not be selected for the 200m when Britain's squad for the World Championships is finalised on Monday.
Pickering (right) wants team-mate Devonish to focus on the 200m
Both sprinters will run in the 100m but Devonish was left out of the 200m to ensure he is fresh for the relay.
"There are loads of athletes who are capable of running under 20 seconds in the 200m and Marlon is not quite at that level," Pickering told BBC Sport.
"But he has run 10.06 seconds over 100m this season so he's right in the mix."
Devonish, 31, won both the 100m and 200m at the trials in Manchester last weekend, but so far UK Athletics have yet to name a single representative for the longer sprint in Osaka.
The Coventry athlete, who won a 200m bronze medal at last year's European Championships, has a season's best of 20.33 seconds over 200m, which ranks him 22nd in the world.
In an ideal world what I'd love to do is run the 100m, and see what happens in the 200m
And Pickering agrees that Devonish is probably best served by only running in the 100m and sprint relay.
"Marlon realises he's got a good chance of making the 100m final and maybe getting a medal," said Pickering. "And we've got a pretty good chance in the relay too.
"The 200m is the weakest event. If he did run the 200m, by the time it got to the relay final it would be his 10th race, and that's pretty tiring."
Earlier in the week, Devonish himself said: "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."
American Tyson Gay, who is the fastest man over 100m and 200m this season, revealed that he was shocked Devonish is not being allowed to double up.
Gay edged out Devonish in a battling performance in Sheffield in July
"It's just not fair that he can't run the 200m," said Gay. "It's the World Championships and the adrenalin is flowing. That carries you a long way."
UK selectors will make the final tweaks to their sprint line-up on Monday, where a third place in the 100m and two further relay spots are up for grabs.
Pickering, who has run 10.14 this season, earned himself an immediate selection by finishing behind Devonish at the trials.
The 20-year-old says selectors have a tough choice to make amongst a crop of British sprinters vying for a place on the plane to Japan.
"Mark Lewis-Francis came third at the trials and so he has shown under pressure that he can run well enough," Pickering said.
"Tyrone Edgar has run 10.13 - which is quicker than Mark has this year, and there's nothing to say Jason Gardener couldn't surprise everyone and get the third spot.
"As far as I know Simeon Williamson (who has run 10.10 this year) has flown out to the World Student Games so it is unlikely he will be picked."
Pickering will also focus on a personal goal in Osaka of claiming the British number one spot from Devonish.
The Bath-based athlete, who was the European junior 100m champion in 2005, is ranked fourth in Britain this season but plans to change that.
"I have been a little bit surprised by Marlon's form," admitted Pickering. "But when he came out and ran 10.06, I knew he'd be a tough competitor.
"It's always been my goal to be the number one sprinter in Britain and in Osaka I'll be looking to run a pretty quick time."
Devonish, Pickering and Day all go over 100m at the Norwich Union Grand Prix at Crystal Palace on Friday.