“No, no, no, no, no.” Danny Murphy’s reaction on TalkSport to reports that Liverpool are interested in signing Shane Long could not have been clearer. In fact, it is probably the clearest that anyone has ever been about Long. You can understand Murphy’s response but it would have made more sense if he had added: “Yes, yes, yes, yes, yes.”

If ever there was a footballer who causes cognitive dissonance, it is Long (no it isn’t), since anyone who has watched him for a significant amount of time becomes totally, disturbingly convinced that he is both a marvellous footballer and not a footballer at all.

It used to be said, and still is by some, that Theo Walcott is just a sprinter in boots. Long may be a hurler in boots, hurling being the Irish sport at which he excelled until switching to full-time football in his mid-teens. His perpetual running, his strength, courage, mighty leap and timing, and the frequency with which he fires the ball over the bar: all of these are traits of an excellent hurler, one reared, like Long, in Tipperary, part of the heartland of hurling.

“Shane didn’t come through an academy … he’s off the cuff. We don’t want to knock that out of him,” said Steve Coppell, the then manager of Reading, who brought Long to England a little over a decade ago. Coppell was speaking in March 2008 after a 2-0 Premier League victory over Manchester City in which Long scored once and generally tore apart a defence that simply could not cope with him. The thinking back then was that if Long retained his speed and wrecking-ball qualities, and topped that off with a surer touch, a bit of footballing savvy and more decisiveness in front of goal, he could be unstoppable. That is pretty much still the thinking now.

Long lost his way towards the end of Coppell’s reign and did not get back on track until Brian McDermott took over at Reading. Indeed, it was at Anfield that the upswing in confidence inspired by the new manager first became really apparent, as Long came off the bench to knock Liverpool out of the 2010 FA Cup. That was the start of what proved to be the most prolific run of Long’s career so far, as he plundered 18 goals in 24 matches for the Championship club.

Shane Long, centre, scores for Reading to knock Liverpool out of the FA Cup at Anfield in 2010 at the start of the most prolific period of his career. Photograph: Carl Recine/Action Images

A year later West Bromwich Albion elevated him to the Premier League. His style endeared him immediately to fans and always deranged opponents. So there was widespread surprise when Albion agreed to sell him to Hull in January 2014 despite being threatened by relegation and in dire needs of goals. Albion fans had come to know, however, that his ball control could range from exquisite (the way he took down a long Chris Brunt pass before blasting into the Aston Villa net in November 2013 is still recalled fondly) to approximate (even now, sometimes when he runs with the ball he evokes a man chasing a pram down a hill). But it was the unsoundness of his finishing that was most maddening, and Albion maintained they were right to accept the bid even after Long returned to The Hawthorns two months later and scored a goal and created another in a 2-0 victory for Hull.

Southampton swooped to buy him from Hull seven months later, Steve Bruce’s club accepting a £5m profit on a player who scored four goals in 15 league appearances for them. He has since registered 10 in 43 top-flight games for Southampton, nearly half of those appearances coming off the bench and many of them being on the wing. Even though Ronald Koeman paid more for Long than for any other forward at the club, the player is not sure to start, or where to start, when everyone is fit. Because Koeman is not sure what he will get from him. Graziano Pellè’s loss of form and subsequent injury gave Long an opportunity to stake a definitive claim but instead he has teased, confirming his potential while compounding doubts.

It has been the same at international level even though the competition for places is less intense. Long has 59 caps and will be one of the first name’s in Martin O’Neill’s squad for the European Championship, yet he started only three of the 11 Republic of Ireland qualifying matches for which he was available and has completed 90 minutes in a competitive international only once in the past five years. It should not have been so, not with Robbie Keane creeping gallantly towards decrepitude.

Shane Long is tackled by José Holebas of Watford during Southampton’s 2-0 win on 13 January. This chance went begging but Long did score one of his team’s goals. Photograph: Mike Hewitt/Getty Images

This season should have been, and may still be, the apotheosis of Long’s career. He turns 29 on Friday, being a couple of weeks younger than Jamie Vardy, the striker who has ripped up the Premier League this term and with whom Long shares many attributes, as Jürgen Klopp has probably noted. Klopp no doubt also saw the Irishman score a sensational winning goal against Germany in October, making his former Borussia Dortmund stalwart Mats Hummels seem like a traffic cone in a tornado, and must have watched Long terrify the defence of the current Premier League leaders while scoring twice in Southampton’s 4-0 victory over Arsenal last month. A YouTube compilation of Long’s greatest hits would definitely rock Klopp’s world but the problem with Long is there are still too many quiet spells in front of goal, or outbursts of swearing at wasted chances. You get why Liverpool may want to buy him but you can also see why Southampton may be prepared to sell him. There was a clue in their purchase of Charlie Austin.

Any Premier League squad would be better with Long in it. He may not, as Murphy said, be better than Christian Benteke but he is definitely different to the Belgian, and to the other players on Liverpool’s and Southampton’s books. He could yet make many important contributions to Southampton. Or they may cash in and sell him to Liverpool, where he could be a forceful addition, especially with so many others out injured. Klopp unashamedly – heroically – advocates fun, high-energy, risky football, and is willing to accept that passes will be mislaid as players try to wreak havoc. If he signs Long, he must accept that lots of chances will be missed. Unless he turns out to be the coach who can finally get Long to improve his finishing the way that Vardy and Walcott have improved theirs. Until that happens, the chances are that Long will remain a player who occasionally makes spectacular impacts but never banishes the doubts.