After both pulled out with foot injuries the team coach, Malcolm Arnold, said: 'It will take a superhuman effort to succeed now.'
The sprint hurdler Jarrett had been called in as a replacement when the world champion Colin Jackson withdrew with a strained hamstring. Wolverhampton's AAA champion, Andy Tulloch, goes in an event which has brought Britain maximum points in the last three Cup meetings.
Arnold said: 'I have great respect for Andy, but this is a killer blow. Our men will have to work tremendously hard to get out of third place.'
Britain, already weakened in the middle distance events by athletes refusing to run because of the demands of a testing season, need to finish in the top two to qualify for September's World Cup at Crystal Palace.
McColgan made herself available for the women's team after nearly two years' absence from the 10,000 metres. But a weekend time trial proved disappointing. 'Her husband, Peter, told me she is just not up to it and reluctantly had to withdraw,' Arnold said.
Fellow Scot Vikki McPherson, who has been on stand-by, takes McColgan's place with Arnold acknowledging Sally Gunnell's team will have to battle to do better than fourth. But a late plus is the return of world 4 x 400m bronze medallist, Phylis Smith, in the relay squad.
Britain's problems were highlighted on a day when the Cup gained an appropriate title sponsor - BUPA - for the first time in a pounds 150,000 deal.Reuse content