Sean arrived at Elland Road after weeks of transfer negotiations for a fee of £500,000 that could rise to £1m based on appearances and promotion bonuses.
The midfielder arrived in Leeds with over 450 games under his belt and the type of experience Blackwell was desperately trying to add to his squad.
The former West Bromwich Albion captain brings real leadership qualities and is an uncompromising, tough tackler.
6ft 2 inch Gregan began life as a defender with Darlington and helped guide them to the old Fourth Division championship (now "League Two") before David Moyes signed him for Second Division Preston North End in a £350,000 move in November 1996.
It was whilst at Preston that he was turned into a midfielder, and made captain. He was voted Preston North End Player of the Year in 1999/00 - the same year he helped them win the Second Division championship (now "League One").
He joined West Brom in August 2002 for £1.5m and quickly became a crowd favourite there too, taking on the captaincy and guiding them back to the Premiership at the first time of asking last season.
Inexplicably he fell out of favour with (now ex-)Baggies boss Gary Megson and that allowed Kevin Blackwell to make his move.
Guisborough-born (Friday 29th March, 1974) Sean once "did a Beckham", scoring from the half-way line, playing against Norwich in March 2001. Only don't tell Neil Sullivan!
Update: November 2006
Sean's Leeds career appears to have come to an end with the
arrival of Dennis Wise. Sean is sent on loan to Oldham, but he has his say before he leaves. Read the news stories, quotes and our analysis:
Wise's First Mistake
7/11/2006 Gregan Interest
Latics sign Sean in un-Wise move
wish the lads well, and I hope they can get out of trouble"