Zeroes and ones.
That’s what Kenny Jackett consistently preaches when it comes to Pompey’s goals-against record.
The boss firmly believes if the Blues concede no more than once per game then they’ll stand a firm chance of being promoted.
In the past two fixtures, however, Pompey have been unable to meet Jackett's demand.
The Blues conceded twice in their defeat to Sunderland on Saturday, as well as three times in Tuesday’s dismal draw with Coventry.
That's stark contrast from last term. It took Pompey until their ninth game to concede twice in a league match - a 2-2 draw with Wycombe on September 22.
The defensive performances at the Stadium of Light and against the Sky Blues certainly underlined there’s a lot found wanting.
As Gareth Evans pinpointed, the collapse against nine-man Coventry was nowhere near good enough.
Yet it’s not a major surprise there have been rearguard flaws at this formative stage of the season.
Matt Clarke nor Nathan Thompson remain at Fratton Park, two players who were mainstays in Jackett's rearguard for the past two campaigns.
Clarke inevitably departed, completing a deserved switch to Premier League Brighton.
Thompson, meanwhile, sought a second-tier club himself after turning down fresh Pompey terms.
While he didn't get his desired move, instead staying in League One with Peterborough, Thompson was regarded as the best one-v-one defender at Fratton Park.
Their departures were always going to impact the Blues.
And not just because of their ability, but they'd built up a rapport with the likes of Lee Brown, Christian Burgess and keeper Craig MacGillivray.
So far this term, Jackett has used eight different players for the four positions in defence – having played only five games in all competitions – and the boss is still searching for his favoured centre-back partnership.
In fairness, Paul Downing’s began the campaign fairly well since his summer arrival.
Sean Raggett, who came in for Christian Burgess, was playing only his sixth match against the Sky Blues. Understandably, he looked rusty.
Burgess, meanwhile, may well have felt aggrieved to have been dropped given he’s barely put a foot wrong.
Right-back has also proved a problem position thus far.
Anton Walkes was axed completely to face Coventry, following a disappointing performance at Sunderland.
His replacement, Ross McCrorie, is primarily a midfielder. After an impressive Stadium of Light substitute cameo, the on-loan Rangers man had good and bad moments against the Sky Blues.
Jackett will be hoping James Bolton can be the remedy when he regains full match fitness. He's a natural full-back who was earmarked to replace Thompson following his arrival from Shrewsbury.
The early defensive performances have unsurprisingly caused angst among sections of fans.
But once Jackett does find his regular back four, you’d expect those coveted zeroes and ones to arrive more frequently.