Donald, 40, even flew over from America for the announcement, despite the fact a back injury will prevent the former world No 1 from playing in the BMW PGA Championship at Wentworth, beginning on Thursday, an event he has won on two occasions.
And he added: "In my time, no-one epitomises the Ryder Cup like Lee Westwood".
"We all know the teams are so well balanced these days that the captain can make all the difference, and he needs all the support he can get".
Westwood said: "I am honoured to have been selected by Thomas to be one of what I think is a pretty impressive quintet of vice captains".
'When Thomas asked me I was obviously delighted and jumped at the chance. Having been fortunate to play in the last ten matches, I am actually looking forward to contributing to Europe's cause in a slightly different way at this year's contest.
"We know what we're up against, we won't run away from it, that's what we've got to face".
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Westwood and Harrington have also expressed an interest in the captaincy and could be rivals to succeed Bjorn and lead Europe in 2020 at Whistling Straits.
McDowell has made four appearances for Europe and famously secured the winning point at the 2010 match at Celtic Manor, where he defeated Hunter Mahan on the 17th hole. The experts at Golfbreaks.com can help with all aspects of your Ryder Cup experience, from accommodation and ticket packages to hospitality and travel and playing some of the fantastic nearby courses.
"Thomas has pulled together a good team here with a lot of knowledge and experience and hopefully at the right times we can give the right words to somebody less experienced than us that might be playing their first one". Memories and relationships that are forged on and off the course those weeks last a lifetime.
This year's event takes place at Paris' Le Golf National from 28 September.
"It is a huge honour to be announced as one of Captain Bjørn's backroom staff and comforting to me that I will be in Paris in some shape or form this year".
And although the Edinburgh-based 45-year-old and his fellow vice-captains could still qualify to face the United States at Le Golf National in Paris from 28-30 September, Westwood (117th) is the only one of the five now ranked inside the world's top 200.