They were a few minutes of hope so brief that the net barely had time to settle before all was dashed again: the time when Carlisle United, having looked dead and gone, pulled back level at Exeter in the 90th minute.

Had the Blues held on at 2-2 until the final whistle, and then found a way to prevail in extra-time, John O'Sullivan's header would have its place among other great, late moments in a club history that already has its decent share.

We know what happened next, Jack Stacey settling the play-off second-leg in the most cutting fashion. It was a cruel finale, with football's emotions at their most extreme, and in O'Sullivan's case he has had a long time to replay all the night's dramatic possibilities in his mind.

It is stark to think that the goal that pulled United level at St James' Park was pretty much the last time the winger touched the ball in a first-team game. An injury in pre-season killed his first three months of 2017/18 and only now, in early November, is O'Sullivan on the brink of returning.

The old stage principle of leaving them wanting more certainly applies with the Irishman. We will soon see a career back out of storage and in time we may discover whether there was something significant in that Exeter moment: an ability to make the strongest statements when the stakes are highest.

O'Sullivan's three United goals to date have all been significant, since his first, at Yeovil, ended a seven-game team scoring drought, before he netted in both play-off legs. The first, against Exeter, was a lucky break, however brightly the winger's eyes may have twinkled when interviewed about the cross that went in, but at the same time, is there not something to be said for a player with the gift of timing?

It could be the case that O'Sullivan has a big-game personality that can benefit the Blues right now. Keith Curle's team are seeking something, someone, to lift them out of some tentative form: not losing much, but drawing often, and certainly not displaying swagger at home.

Much has been tried, in tactics and selection, but one or two options have been lost to the manager for much of the campaign. Without investing too much expectation in someone who will need time to get back up to first-team speed, why not hope that one of those options could provide something refreshing?

The continued physical ordeal of Jason Kennedy has been this season's biggest regret so far. The midfielder was a linchpin of United's best form last term and Carlisle never seem to look quite so compact, or reliable, when he is not there.

Is it also, though, possible to miss a player who has made just 10 starts and nine substitute appearances, while enjoying just five victories?

Maybe you can, when Carlisle's current requirement is for purpose at the top end of the pitch at Brunton Park. O'Sullivan is a punchy runner down the right wing and has a demeanour that suggests he doesn't mind a confrontation, in the right way.

We did not get much opportunity to discover how consistent he could be in a United shirt last season, since Curle was just as happy to use the 24-year-old as a substitute; his two Exeter goals came in this way, both occasions when he helped change the tone of matches which had been drifting away from the Blues.

And no doubt this is how he will be fed back in. At the same time, Carlisle did not make him one of their key signings last January to be held back for the last half-hour of games. They invested in a promising pedigree and a bright background with Blackburn Rovers, and a career that required the proving ground of League Two in order to gain momentum.

Belief never seemed a deficiency in O'Sullivan. A bright personality and willing talker, he came across as someone who felt like he had the right to be on the stage and possessed qualities that could lift the Blues.

A squad can be built from different parts but a team need not get out of bed unless it has at least a few players who believe they should be there, who back their ability, who think they are good enough to push the ball past any left-back you choose and rip over a cross or a shot.

Add to this the feeling of pulling at the leash for six months, and it's unlikely you will have someone content to drift quietly through the next phase of Carlisle's season, once he is back.

The suspicion that a player has a big-game temperament is not always a cast-iron guide. The moment that settled United's decision to sign Danny Carlton in 2007 was the goal he scored to send Morecambe into the Football League (also a play-off strike against Exeter, as it happens).

Neil McDonald's hunch did not lead to a Blues career of substance for Carlton. Maybe a difference in O'Sullivan's case is that the manager who signed him is still here, and one would hope the same faith that put an 18-month contract his way also remains; likewise the confidence that was rewarded with those moments against Exeter.

This campaign has been no picnic for United. It has left them in an underwhelming position, 16 games in, and in need of a revitalising cup run, which they will attempt to launch against Oldham today.

A season can be kickstarted in other ways, too, and an attack-minded player bursting back onto the scene in late autumn is one of them. There are no guarantees, and lots more that Carlisle need to get right, but maybe a fit O'Sullivan could give them at least a shot of what they need.