Portsmouth 4 Northampton 1: Neil Allen's verdict - Red card sideshow shouldn't overshadow display worthy of League One champions

The transfer window had reinvigorated flagging belief, substantially reinforcing a squad theoretically capable of securing a Championship return.

Yet Northampton delivered tangible proof. No mealy-mouthed words, grandiose promises or bold claims - simply a powerful demonstration of promotion potential. On the pitch, where it matters.

Buried beneath the distractions of Tom McIntyre's controversial red card and accompanying furore was a gem of a Pompey performance which must not be overlooked.

Granted, the debut defender's dismissal was a shocking piece of officiating, nonetheless it shouldn't be allowed to divert attention away from a brilliant showing from John Mousinho's men.

Since the magnificence of Bolton in December, displays have been fitful and largely functional. The occasional quickening of the pulse, but all rather run of the mill.

Workmanlike victories, mundane draws and shock defeats hardly befit a team perched at the top of League One for 19 of the last 20 weeks. Champions should flirt with the spectacular rather than embrace the solid.

However, on Saturday, Northampton were the poor unfortunates to feel the full force of impressive January window dealings as a revitalised Blues ruthlessly tore them apart.

Mousinho's men plundered four goals, yet there was also a disallowed effort, a missed penalty, and a goal-line clearance during a rampant showing oozing attacking menace and delivered with a spellbinding swagger.

Improbably, two of Pompey's goals were registered after being reduced to 10 men, with the outstanding Callum Lang at the heart of both during a dazzling second-half display.

This time last week, sporting director Rich Hughes was putting the finishing touches to the versatile attacker's switch from Wigan. Now he's suggesting he could be the promotion catalyst they have craved.

Lang was among four changes from the side denied victory at Oxford United in heart-breaking circumstances, representing a first start for his new club, with fellow fresh face McIntyre joining him in the line-up.

With fit-again Joe Rafferty restored at right-back and Tom Lowery replacing the injured Joe Morrell in midfield, Mousinho flexed his squad strength in depth, with numbers bolstered five January newcomers.

As a team, there was a welcome zip and high tempo to their play, eradicating the tiresome penchant for defenders exchanging passes for long periods while entrenched in their own half.

Driven on by the directness of Lang, Paddy Lane and Myles Peart-Harris, a high-octane Blues operated on the front foot. They poured forward, hunting in packs, displaying a boundless energy which barely dipped.

Indeed, both of Lane's goals arrived from rapid counter-attacks, largely an untapped source this term with build-ups usually far too laboured, particularly over the last two months.

Pompey have remained top of League One throughout their post-Christmas blip, while, in recent weeks, have ticked over satisfactorily after rediscovering that precious winning touch. Yet never with a performance of this calibre.

On Saturday, the Blues looked every inch a side destined for the Championship - it was wonderful to witness.

Invariably netting twice in the opening 16 minutes helped their cause, dictating the game's pathway early on, yet pursuit of more goals was admirably relentless.

Pompey opened the scoring on seven minutes when Conor Ogilvie stooped to head home Marlon Pack's right-wing free-kick and then, nine minutes later, the skipper produced a sublime diagonal ball to turn defence into attack.

That picked out Lane on the right flank, who surged forward and cut inside onto his favoured left foot to curl home a delightful finish to make it 2-0.

Before the half had ended, Peart-Harris, operating on the left flank for this game, was pushed inside the box, only for Colby Bishop's penalty to be saved by Lee Burge diving to his left.

Then, on 54 minutes, McIntyre beat Mitch Pinnock to the ball to clear left-footed, only for the players to catch each other. The linesman alerted referee Sam Purkiss, who baffling dismissed the Pompey player on his debut.

Within four minutes, Lang cleverly intercepted a Cobblers free-kick to initiate a lightning break upfield before squaring to Lane, who took a touch before crashing home a fierce left-footed shot from outside the box.

The hosts still weren't finished, however, with Pack's 71st-minute free-kick delivered from the right and Ogilvie's header dropped invitingly for Lang to volley home right-footed and make it 4-0.

Northampton's Marc Leonard's thunderous first-time right-footed shot from outside the box in the dying minutes provided late consolation.

It would have been a worthy winner for any game, but not that day, not against that Pompey team. On that form, nobody in League One could match the Blues - now they must continue producing it in the final 15 matches.