The club have only 300 tickets left for the game down at Roots Hall from an allocation of nearly 2000.
It will be Wednesday's second consecutive long-distance road trip following on from the club's last outing - a 2-1 win at Plymouth on September 19th.
Sales for the Hull game the week after are not going that well but the game is on a Friday night and on Sky television - so far only a quarter of the 2500 tickets have been sold.
Meanwhile three players were on international duty this weekend while the rest of the squad took a break.
Madjid Bougherra'a Algeria drew 0-0 with Guinea in an African Nations Cup qualifier, Glenn Whelan's Ireland Under-21 team lost 1-0 to Belgium but Chris Brunt was not even on the bench for Northern Ireland's 3-0 defeat to Iceland.