Thomas became known for his performances of the Ayatollah whenever he scored for his club or country and the former Wales captain has always made no secret of his support of the Bluebirds.
And Purse – a big friend of Thomas – said that he has received a phone call to say that Cardiff must come out on top in the Carling Cup clash on Tuesday night at the Liberty.
Purse said "Alfie's a massive City fan – he always does the Ayatollah when he scores a try.
"I went to his testimonial dinner at the end of last season because my son, Luca, has become a big rugby fan since moving to South Wales.
"I've taken him to watch Cardiff Blues against the Ospreys, the rugby version of Cardiff-Swansea.
"Alfie's a great lad and I've been keeping in touch with him over the last few weeks. He's spoken to me about Tuesday's game and he wants us to win as much as any Cardiff supporter."
"Nobody at the club has played in a South Wales derby but we know what this game means to our fans. I know what it means to them because ever since the draw was made I've had loads of them coming up to me and saying 'You can't lose to Swansea'
"We know this game is the one our fans are talking about and we have to produce a performance that makes them proud of us. But it's not just about beating Swansea – we want to be in the fourth round.
"I've not played in a Cardiff-Swansea derby but I'm sure it will be a great game to play in. I'm really looking forward to it.
"This will be the first time the clubs have met for nine years so that's going to make Tuesday's game even more special.
"There are games that live in your memory and you tell your grandchildren about. I played in a lot of Midlands derbies when I was up there and they were fantastic."