|Glasgow 2014 Commonwealth Games|
|Dates: 23 July - 3 AugustCoverage: Live on BBC TV, HD, BBC Radio 5 live, Red Button, Connected TVs, online, tablets and mobiles|
Banned Welsh 400m hurdler Rhys Williams would not "knowingly" take drugs, says ex-Commonwealth Games silver medallist and compatriot Christian Malcolm.
Williams, 30, will miss Glasgow 2014 after failing a drugs test, with countryman and 800m runner Gareth Warburton absent after he was charged with anti-doping rule violations.
Both Williams and Warburton, 31, deny deliberately taking banned substances.
Malcolm said Williams, whom he has known for 18 years, was "anti-drugs".
He added: "I know Rhys wouldn't have knowingly taken drugs."
Matt Newman, chief executive of Welsh Athletics, said his organisation was "not taking this lightly".
"It is without doubt the worst two weeks that I've been through in seven years in charge of athletics in Wales," he said.
"We're reflecting on what this means not just for the athletics team, but for the whole of Team Wales, who have had a series of disappointing announcements over recent days."
Williams, the son of former Wales and Lions rugby player JJ Williams, tested positive at the Glasgow Grand Prix on 11 July.
The 2012 European champion has been banned from all competition by UK Anti-Doping pending a hearing.
Williams, co-captain of Wales' athletics team, said he was "utterly devastated" by his positive test.
Malcolm, 35, said: "He's always been a big fan of athletics. He's been a great ambassador for Welsh athletics in recent years.
"He's had his difficulties, his ups and downs through injuries, and he's fought back very well. So for him to have a blow like this in his career is just sad.
"Rhys is a proud guy. He is always someone who's been anti-drugs."
Malcolm, who won silver at the Kuala Lumpur Commonwealth Games in 1998 and was twice a bronze medallist at the World Championships, added Williams would be under intense public scrutiny.
"Fortunately for Rhys, he's got good family, he's got a good circle of people around him and hopefully they can give him the support he needs right now," said Malcolm.
"I just hope, for his sake, they'll be able to get to the bottom of this and find out what happened."
|Rhys Williams's medals|
|2006: 4x400m hurdles silver, European Championship||2010: 400m hurdles bronze, Commonwealth Games|
|2010: 400 hurdles silver, European Championship||2012: 400m hurdles gold, European Championships|
BBC Sport understands the manufacturer of 'Mountain Fuel', a sport supplement used by Williams, is co-operating with the athlete to see whether any of its products are responsible for his failed drugs test.
The company is also believed to be undertaking its own internal tests to establish whether any banned substances were inadvertently used when making the product.
'Mountain Fuel' is thought to be just one of a range of products used by Williams that are being examined.
The results of the tests are expected on Wednesday, with sources close to the company claiming it is confident of being exonerated.
The suspension is a further blow to Welsh medal hopes in Glasgow, which have also been hit by injuries to key competitors including triathletes Non Stanford and Helen Jenkins, and cyclist Becky James.
Team Wales also lost Olympic silver medal-winning boxer Fred Evans, whose accreditation was refused because of his conviction for assault in a nightclub in April.
Newman is to launch his own investigation into what happened.
Wales have been set a target of 27 medals for Glasgow 2014 - eight more than they won at the 2010 Games in Delhi - but Newman thinks this may have to be revised.
"There is a medal target both for athletics at the Games and for the whole of Team Wales," he said.
"This will undoubtedly impact on those medal targets."