In their second meeting of the season, Ronald Koeman made several changes to the starting XI, with Nathaniel Clyne inserted back into the lineup. There was also a debut for Eljero Elia, at the expense of Duśan Tadić.
The first half was a rather dull affair as neither side could even muster a shot on target. Southampton started brightly when Nathaniel Clyne, who made his first appearance since Boxing Day, sent a shot wide across David de Gea's goal.
Southampton then was forced into making a substitution as Toby Alderweireld had to come off with an injury after making an interception. The Belgian was replaced by Florin Gardos.
José Fonte then had a chance to put his team in front, but his header following a short corner routine was off target. The last few minutes of the first half saw the host asserting themselves into the game, with Angel Di Maria racing into the box but his cross was too close to Forster who grabbed it gleefully as the first half came to a close.
The second half saw the visitors cranked up the pressure but to no avail as attempts from Graziano Pellè missed the target (a common theme throughout the game).
But the host did not fare better as Phil Jones headed over the bar from Wayne Rooney's free kick as the score remains goalless heading into the last 30 minutes.
Elia was then taken off in the 62nd minutes, with Tadić coming on and boy, did that substitution worked like a charm.
Pellè was through on goal and though his shot beat De Gea, it struck the post, fortunately the ball fell to Tadić who slotted it past United's defenders to give Southampton the lead.
Despite a late barrage of attacks from the host, Juan Mata in particular, had three attempts in the last 15 minutes or so, but did not managed to trouble Forster, The Saints held firm to grabbed all three points and climbed up to third place.