Carlisle United 0 Sheffield Wednesday 0: The key moments in this intriguing goalless draw seemed to happen in slow motion. That both eventually went against the attacking sides tells you why we are where we are: with Carlisle United and Sheffield Wednesday both in tonight's fourth round pot.

First, when Liam Palmer's cross attracted Atdhe Nuhiu's head like a magnet little more than a minute in. It was a moment that could have exposed a two-division gulf painfully early in this FA Cup tie.

The crossbar, though, reprieved Carlisle. At the same end of the pitch an hour or so later, the margin was again thin, this time the few inches of space between Sam Cosgrove and Wednesday's defensive line, as he buried a convincing header past keeper Joe Wildsmith.

The offside flag denied United's inexperienced striker hero status. Cosgrove later said the "split-second" before he realised it had been chalked off had seemed to last longer than usual.

That's understandable. Anyone so close to marking a fourth senior start with a goal that could have put a Championship team out of the cup could be forgiven for a few moments' dwelling on it. So early into a first-team career which has suddenly launched into life in 2018, 21-year-old Cosgrove is already learning how games like this can exist on a knife-edge.

The tie in general remains on pause, a predicament United will enjoy more than Wednesday. Cosgrove, as Keith Curle's target man, did well, showing good hold-up play and a quality touch, but the substance of this result came further back, where Carlisle's defending was on the button and Mike Jones excelled in midfield against a second-tier team who are currently strangers to the winning habit.

Lee Bullen, the Wednesday caretaker, will hand over a team that appears to need jump-leads to new manager Jos Luhukay. Some of their individual qualities were obvious at times on Saturday but after one victory in 10 they lacked the overall zip of a team in form.

Carlisle's hope will be that the Blades of Sheffield United hand Luhukay a blunt welcome next Friday before the replay four days later. If the new-manager bounce arrives early, the Owls will be expected to fly through to the fourth round at the second attempt. If not, United cannot be discounted, particularly given their liking for taking on bigger opponents in the cups under Curle.

Once again in a knockout competition, United performed well enough to make it easy to understand why fans have been infuriated by their league form. They were compact and organised, often tenacious in the challenge, and while they did not exactly run rings round Bullen's defence, they did put them on the back foot a time or two when their confidence increased.

Doing it again at Hillsborough will be a challenge but before then it is just as important that United bring these qualities to the table against Crewe, in League Two. Their error count was low against Wednesday, as it had not been at Mansfield and against Coventry; that has to be the starting point for their efforts from here.

Given the importance of the manager's talks with the board - set to resume early this week - it felt like a day whose significance rose above the norm, even accounting for the third round weekend's usual buzz. Regardless of how much heed one pays to the fans who brought a "Curle Out" banner to the Pioneer Stand (the manager later offered to meet them to discuss their issues) plenty is under scrutiny at Brunton Park right now.

The club needs all the good days it can get; this was one. The crowd figure (7,793) was by no means sensational but most of those in the ground certainly responded once United found their feet in the tie. The early period saw them survive Nuhiu's early chance, and while Cosgrove won his share of headers at the other end, the ball was mainly at Wednesday toes to begin with.

Lucas Joao's pace threatened to slice United open on the break, but never fully did. Ross Wallace's ball-playing threatened to find gaps unavailable to others, but never fully did. Nuhiu looked a physical customer but Clint Hill, on career appearance 650, rolled the years back comfortably enough.

Carlisle were very deep from the outset, only occasionally venturing down the right side, which seemed their most productive area. Wednesday came onto them but had to make do with half-chances. One, from Nuhiu, was saved by Jack Bonham. Another saw the forward denied by a Gary Liddle slide.

George Boyd, who used to enjoy tormenting United in a Peterborough shirt, only flickered on his return from injury. Going the other way, Curle's side became steadily more adventurous, especially when James Brown bustled down the right and fed Hallam Hope, who swept past a defender and shot narrowly across goal.

This was Carlisle's best work so far, and it was a shame they did not make more of a few free-kicks that came their way before the break. Wednesday, meanwhile, toiled to make the most of their passing and movement, their final ball lacking quality, Adam Reach at times the culprit, while Hill and his fellow defenders cleared their lines.

Once or twice when United took longer to do so, anxiety could be heard in the stands, likewise when Wednesday started the second half at a sharper tempo. This was the spell that could have made the difference but Joao and Boyd could not capitalise on some persistent pressure. Joao got closer on 59 minutes, but his header from Dan Jones' free-kick hit the outside of the post.

The moment that would have asserted Championship superiority never quite came. Wallace, through whom much of Wednesday's better work flowed, went close from 25 yards after United were pressed into errors. Bullen then sent Jordan Rhodes on from the bench to try and capitalise on this momentum, but it was Carlisle who almost prised the tie open.

Their doggedness on the right kept an attack alive, and when Jamie Devitt eventually crossed and Cosgrove steered it past Wildsmith, a famous story seemed as though it might be getting written.

No such luck. After that was chalked off, Wednesday went close again through Nuhiu, as Bonham reacted superbly to keep out his downward header. Tom Parkes got in the way of another Wallace shot but then Carlisle almost found another way through as they saw more of the ball, Devitt this time unable to get it out of his feet after Lambe sent him chasing through on goal.

At both ends, but especially United's, there were other forays that didn't get quite so far, because they were intercepted early enough by alert defenders. It says much about this perplexing season that Carlisle have managed only three clean sheets at Brunton Park, yet one of them has come against a side 45 places higher in the EFL.

Answers on a postcard as to which direction it all goes in next. To still be in the cup beyond January's first weekend, though, is positive on its own merits. It says the Blues rose solidly to this challenge - and, in Cosgrove's case, almost enjoyed a moment for all time.