United were in east London for their FA Cup first-round meeting with Orient on Saturday afternoon.
The Cumbrians bowed out of this season’s Emirates FA Cup competition at the first-round stage as they fell to two second half sucker punches, having got themselves into a position where they looked to be edging on top.
And more of a concern was what looked to be a horrible injury for Callum Guy which left him needing a stretcher and a trip to an East London hospital.
The game started with the 463-strong travelling support in good voice, with manager Paul Simpson having made just one change to the starting eleven from last weekend with Jack Robinson in for the suspended Jack Armer.
Keeper Jokull Andresson was cup-tied by parent club Reading, so Gabe Breeze stepped up, and Paul Huntington missed out through a sickness bug which had struck him down through Thursday and Friday night.
Fin Back was still absent, and that meant that Ben Barclay continued on the right-hand side of the back line.
Carlisle started brightly as they tested the box with deliveries and Mellish asked Brynn a question when he jumped to meet a delivery from Guy. The downward header was on target but the keeper got in the way.
Defender Sam Lavelle caused a scramble when he got on the end of another decent set piece, but the same player was left with his head in his hands when he was judged to have fouled Dan Happe with just 11 minutes on the clock.
He protested that he’d been tugged off balance, hence the reason for the raised boot, but referee Seb Stockbridge pointed stubbornly at the spot. Joe Piggott stuttered his run-up and sent Holy the wrong way as he found the bottom corner.
The afternoon took its worst turn for the away side when Guy went down three minutes later, clearly in agony. A prolonged period of treatment followed before he was led off to the waiting ambulance. That brought McGeouch into the fray somewhat earlier than had been planned.
United may have been rocked but an incisive move put Butterworth into space. He strode forward and unleashed a blistering effort, but it struck Joe Garner and bounced away to safety.
Jordan Gibson was next to tease a lovely ball forward and Sean Maguire showed good movement to get on to the beautifully flighted pass. He looked to guide his second touch over his shoulder but it rose too high and dipped over the bar.
Half chances came and went for both teams ahead of the break, and Simpson looked to shake things up for the second period when he brought Whelan on for Butterworth and pushed Mellish into the midfield berth.
It appeared to work as blue shirts flooded forward, and Mellish found room to turn and slide a pass to Garner, who was sprinting towards the edge of the box. A stinger of a drive was going in until Brynn dived long to parry.
But the stranded stopper could do nothing when Barclay crossed from the resulting throw. Garner was unmarked and he calmly guided the equaliser over the line.
United looked confident, and Moxon pulled a shot wide as more intricate play once again opened things up. The movement was good, and the energy levels high, but the wind was taken out of the sails when James gambled on a lobbed, sweeping delivery into the box. Drinan had also chanced his arm and he celebrated in front of the home end when he tumbled his way to meet it and bundle it underneath Holy.
Carlisle’s keeper saved low from the same man moments later, and watched on in relief when Garner, back for defensive duties from a free kick, miscued a clearing header onto his own bar.
Home pressure mounted and Drinan was denied a further time when Holy leaped at his feet to block what would otherwise have been a simple finish.
The O’s sealed their progression on 90 minutes when Sotoriou pounced on hesitation in midfield to scamper free and clear. A bullet of a finish rifled through Holy’s legs.
Leyton Orient - Pigott (11 pen), Drinan (66), Sotiriou (90)
Carlisle United - Garner (50)
Leyton Orient - Cooper (8), Forde (14), El Mizouni (60), Happe (70), Sweeney (90+6)
Carlisle United - Robinson (72)
Leyton Orient - Brynn, James, Turns, Happe, Cooper (Sweeney 64), Brown, El Mizouni (Pratley 90), Galbraith (Moncur 77), Archibald, Forde (Drinan 46), Pigott (Sotiriou 77). Subs - Howes (gk), Beckles, Pegrum.
Carlisle United - Holy, Barclay, Robinson, Lavelle, Mellish, Guy (McGeouch 20), Moxon, Butterworth (Whelan 46), Gibson (Plange 83), Maguire (Ablade 77), Garner (Edmondson 83). Subs - Breeze (gk).
Referee - Sebastian Stockbridge
Assistant Referee 1 - Garry Maskell
Assistant Referee 2 - Ryan Head
Fourth Official - Harry Wager
Observer - Michael Bull
Attendance - 3,808 (463)