After a morning frost delayed the start of the second round by over two hours, Casey's afternoon tee time assured him that he wouldn't finish the round on Friday.
Casey made the most of his opportunity, however, especially after his challengers were only able to overthrow his lead momentarily.
The 26-year-old birdied the opening hole to regain a share of first. At the par-4 fifth, Casey ran home a 20-foot putt for a birdie and landed his approach just off the putting surface at the par-4 sixth.
Casey ran home the birdie putt from the fringe and made it three in a row with a birdie at the seventh to move to 12-under.
Casey then birdied the par-5 14th shortly before play was called to stand at 13-under par.
Several players were able to complete their rounds of Friday, including 1999 British Open champion Paul Lawrie.
Lawrie ran off seven birdies and no bogeys to stand in the clubhouse at 9-under-par 133.
'I now feel the best I have for two or three years,' said Lawrie, who has struggled through multiple injuries this year.
Fellow Scot Stephen Gallacher fired a 64 of his own for his share of the clubhouse lead while Australia's Peter Fowler joined the duo at minus-9 after a round of 66.
Nick O'Hern and Marten Olander finished knotted at 8-under-par 134. Local favorite Sergio Garcia managed an even-par 71 to join Angel Cabrera at 7-under-par 135. Robert Karlsson of Sweden stood at 7-under par through 16 holes when the round was called.
Play will resume Saturday morning with the 36-hole cut to follow. Defending champion Steen Tinning, who will be retiring after this event, is currently 1-over par through 15 holes.
European Tour veteran and 1988 Masters champion Sandy Lyle, who needed to finish in the top-nine this week to secure his card for 2004, withdrew from the tournament due to an illness.