A quality Michael Bridges strike gave the Cumbrians victory over second placed Grimsby but the nervy match failed to live up to it's table top billing.
Bridges goal, his 13th of the season, was an exception. Latching on to Zigor Aranalde's inch perfect through ball the former Premiership hitman drew the keeper before lifting the ball over him and into the net.
Both sides had appeared more worried about losing than winning the game and it was a quarter of an hour before the first real attack of the match. Karl Hawley beat the offside trap of the visitors and raced to the by-line but his cross for Bridges was plucked out by Steve Mildenhall.
Bridges was the liveliest attacker beating three defenders in the 22nd minute before he was crowded out in the box, but he came closer in the 35th minute when Aranalde played him into the box and he skipped past two markers to fire a shot that the keeper gathered at the second attempt.
Grimsby's powder puff strike force rarely threatened Keiren Westwood but the young United stopper did turn away a Marc Goodfellow shot after the Mariners played a neat 1-2 with Michael Reddy just before the break.
Andy Parkinson did test the United keeper with a tame shot just before Carlisle struck but he forced a good save from Westwood when Kevin Gray's clearance fell to him on 67 minutes.
Last week's Millenium Stadium scorer Adam Murray replaced the injured Danny Livesey and fellow sub Simon Hackney raced down the left wing to cross for the midfielder to fire in a crisp header that Mildenhall did well to stop. Karl Hawley had chances to add to his 25 goal tally and should have doubled the hosts lead in the 76th minute but he wanted too much time and danger was snuffed out and he was unlucky late on when Murray played him in with a precision pass but his shot on the turn was tipped over.