Rochdale 0 Carlisle United 1: John-Kymani Gordon's early goal was enough to earn Carlisle a third straight win at Rochdale.
The Crystal Palace loanee struck after just eight minutes at the Crown Oil Arena.
And the promotion-chasing Blues held on against League Two's bottom side, who had a late Ian Henderson goal disallowed.
The latest United victory keeps them fourth in the table, as third-placed Northampton Town also won at Barrow - but they are now six points above fifth.
It was a far from comfortable victory against Jim Bentley's strugglers, who gave Carlisle some anxious moments in the second half in front of 1,634 travelling fans.
But an 11th clean sheet of the season kept the Blues' promotion challenge very much on track.
Blues boss Simpson named the same XI and subs as he did for Tuesday's 3-1 victory over Hartlepool United, whilst Rochdale made four changes, new loan signings D'Mani Mellor and Owen Dodgson getting debuts and Jim McNulty and James Ball also coming into Bentley's line-up.
Carlisle made a rapid start and could have scord as early as the second minute when Gordon ran at the home defence, but took the ball too wide and was denied on the line.
At the other end the Blues dealt with a dangerous Femi Seriki run from the Rochdale right - before breaking to take the lead.
Kristian Dennis, dropping off, was the supplier, and his pass sent Gordon clear of the defence to shoot low past Jake Eastwood.
It triggered big celebrations in the bumper away section.
And Carlisle looked confident in their pursuit of more goals, Dennis shooting wide from outside the box and an Owen Moxon corner almost setting up Jordan Gibson.
United looked to send the ball forward early to force the pace in Rochdale's half, while Bentley's side tried to threaten through Devante Rodney and new boy Mellor, who got past Paul Huntington and was brought down.
That led to the first of three bookings for Carlisle in the first half, Morgan Feeney later cautioned by ref Ross Joyce for dissent and Gordon for an off-the-ball incident with Jim McNulty.
Rodney shot against Tomas Holy's legs for the hosts, with Dennis sending another attempt wide, with clear-cut chances scarce.
The hosts were forced into a change on 40 minutes as the injured Liam Kelly had to be replaced by Toumani Diagouraga.
Moxon sent a 35-yard free-kick over the bar in first-half added time as Carlisle reached the interval 1-0 up.
After the break, Callum Guy shot just wide from outside the box before Mellor couldn't make the most of a back-post header for the hosts.
Rochdale were then denied a penalty when Rodney went down after cutting in against Feeney.
Things remained in the balance, Carlisle unable to pull clear of their struggling hosts, and Simpson looked to freshen things up with the introduction of Omari Patrick for Gordon just after the hour mark.
United broke promisingly through Gibson and Joel Senior, but the latter's cross from a good position was blocked.
After Dennis couldn't finish a Jon Mellish cross, Rochdale made three substitutions on the 74-minute mark as they sought a late way back.
Scott Quigley and Henderson joined their attack while the third sub, Abraham Odoh, forced a flying save from Holy with a 30-yard attempt.
Simpson then introduced Joe Garner and Alfie McCalmont for the closing stages, Quigley then shooting high over the bar for Dale after cutting in from the right.
Dodgson had a further opportunity, cutting in from the left after the hosts switched play, but he couldn't keep his shot down as he aimed for the top corner of Holy's goal.
Rochdale then thought they had levelled in the 88nd minute when Henderson applied the finishing touch from close range.
But their celebrations were cut short by the assistant referee's flag as it was ruled out for offside.
A late attempt from Tyrese Sinclair was blocked as Carlisle managed to hold on for the victory.
Rochdale: Eastwood, Seriki, McNulty (Odoh 74), Taylor, Kelly (Diagouraga 40), Ball (Sinclair 86), Mellor, Rodney (Henderson 74), Keohane, Dodgson, Lloyd (Quigley 74). Not used: O’Donnell, John.
Booked: Lloyd, Diagouraga.
United: Holy, Feeney, Huntington, Mellish, Senior, Armer, Guy, Moxon, Gibson (McCalmont 78), Gordon (Patrick 62), Dennis (Garner 78). Not used: Kelly, Whelan, Devitt, Robinson.
Goal: Gordon 8.
Booked: Huntington, Feeney, Gordon.
Ref: Ross Joyce.
Crowd: 4,042 (1,634).
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