Hussain, a candidate for Mike Atherton's England job, will take over the Essex reins in the absence of the injured Paul Prichard, who tore a hamstring during his double century in the last Championship match against Kent and could be out for a fortnight.
Hussain was Atherton's deputy on the winter tours to Zimbabwe and New Zealand and has established himself in England's top order.
Prichard's absence leaves Hussain with an opening problem, but Graham Gooch will not be tempted to make a romantic return as Essex bid to reach Lord's on 6 September and erase the memory of last year's final when Lancashire dismissed them for 57.
Darren Robinson will probably open the innings with the Tim Hodgson slotting in lower down in the order.
Glamorgan's only 60-over final appearance was in 1977, but their hopes of a one-day title was spoiled by a five-wicket Middlesex victory.
This time, they have a potential match-winner in Waqar Younis, who said: "Essex are not an easy team to play against. They have a good bowling attack, and some excellent batsmen but if we play to our full potential we are a match for anyone.
"It all comes down to what happens on the day, of course. If we play well I don't think there is anything they can do to stop us going to Lord's."
Matthew Maynard, the Glamorgan captain, added: "Essex will favour their batting, they will look to bat us out of the game if they get in first but if we show the character we showed against Hampshire and Yorkshire, we will be all right."
Maynard made 78 and England's Robert Croft 50 when Glamorgan beat Essex in their last NatWest meeting in Cardiff in 1994. The Welsh county will be more than happy to settle for something similar, but Essex may be able to produce something special.Reuse content