The visitors, meanwhile, moved back into the play-off spots by dispatching Bristol Rovers at the weekend.
Match preview
After gaining promotion by beating Stockport County on penalties in last season's League Two play-off final, Carlisle were always likely to find life in the third tier a little tough.
Despite only winning one of their opening 10 league games, Paul Simpson's side will head into their home match against Peterborough outside of the relegation places, although Reading and Wigan Athletic do possess a game in hand each.
Indeed, those two teams' respective points deductions have also helped Carlisle avoid being in the bottom four places at this early stage of the campaign, with Simpson's side powerless to prevent their fifth defeat away to Wycombe Wanderers last time out.
Jokull Andresson's 29th-minute dismissal left the Cumbrians with a mountain to climb, with Luke Leahy's penalty and Sam Vokes' strike either side of half-time duly punishing their opponents, who will need a much better performance if they are to avoid defeat on Tuesday.
After all, Peterborough will expect to be fighting at the upper end of League One once again, following their dramatic defeat to Sheffield Wednesday in last season's play-off semi-final.
Darren Ferguson's side had beaten the Owls 4-0 at home in the first leg before throwing that lead away at Hillsborough in the reverse leg, ruining their chances of bouncing straight back to the second tier as a result.
However, Posh began the campaign with a vengeance by winning each of their opening three fixtures, while eight points from their last four matches has helped them recover from a slightly stickier patch of form.
Ferguson will have been delighted to see his side keep a clean sheet against Joey Barton's dangerous Bristol Rovers outfit at London Road Stadium when beating them 2-0 on Saturday, and he will be demanding the same from his players once again ahead of a long trip to Cumbria in midweek.
Carlisle United League One form:
L
W
D
D
L
L
Carlisle United form (all competitions):
W
L
D
D
L
L
Peterborough United League One form:
L
L
D
W
D
W
Peterborough United form (all competitions):
W
D
W
D
L
W
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Team News
Carlisle will be forced to replace Andresson - who is on loan from Reading for the season - in goal after his dismissal against Wycombe, with former Ipswich Town stopper Tomas Holy set to start.
Alfie McCalmont and Joe Garner will both be hoping to be called upon from the outset after only being used from the bench during their side's defeat.
Peterborough, meanwhile, will travel without Jeando Fuchs due to an ongoing groin issue, with Ferguson likely to be tempted to name an unchanged starting XI after beating Bristol Rovers in their last match.
Jonson Clarke-Harris will be desperate to get himself on the scoresheet having only bagged four times in nine league games, which represents a downturn from his previous efforts at this level in terms of a goals-per-game rate.
Carlisle United possible starting lineup:
Holy; Back, Lavelle, Huntington, Mellish, Armer; McCalmont, Gibson, Moxon; Garner, Plange
Peterborough United possible starting lineup:
Bilokapic; Katongo, Knight, Edwards, Burrows; Kyprianou, Collins; Ajiboye, Mason-Clarke, Jones; Clarke-Harris
We say: Carlisle United 0-2 Peterborough United
Peterborough have taken only two points from their last three games, but we expect them to better that tally on Tuesday alone by beating Carlisle.
Simpson's side look like they may be lacking quality in order to survive at this level, but they will continue to fight hard and will not make things easy for their opponents.