A Ben Burgess penalty on the stroke of half-time was enough to give Blackpool all three points away at Southampton.
Burgess coolly sent Saints goalkeeper Kelvin Davis the wrong way to slot home from 12 yards after Gareth Taylor-Fletcher had been fouled in the box.
Blackpool captain Rob Edwards twice cleared off the line, while the visitors had three goals disallowed.
David McGoldrick hit the bar late on as Southampton rallied, but they could not find a way past Paul Rachubka.
Southampton head coach Jan Poortvliet:
"I expected more from the players and when you look at the game as a whole they deserved their win.
"After the break we did not have enough power and may be it was a little bit too much for our young guys after playing two games in a week.
"We looked vulnerable in defence and we played too much to give a show but we have to play to get winning results."
Blackpool boss Simon Grayson:
"There were a lot of chances for both teams but we are delighted to get all three points.
"There were several blocks and they hit the woodwork and the way our season is going you thought that Southampton would get an equaliser.
"But credit to my players because they dug in deep and we deserved the win."
Southampton: Davis, James, Svensson, Perry, Surman, Gillett (Wotton 68), Lallana, Schneiderlin (John 67), White (Dyer 46), McGoldrick, Holmes.
Subs Not Used: Bialkowski, Cork.
Booked: Surman, Gillett, James, Svensson.
Blackpool: Rachubka, Barker, Edwards, Evatt, Camara, Taylor-Fletcher (Coid 86), Fox (Rehman 81), Jorgensen, Hammill (Vaughan 67), Burgess, Kabba.
Subs Not Used: Gilks, Aluko.
Booked: Camara, Burgess.
Goals: Burgess 45 pen.
Att: 15,629
Ref: Andre Marriner (W Midlands).
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