There are remarkable coincidences, outrageous quirks of fate which cannot be explained.
That fact Pompey have never won a league fixture without Tom Naylor since his Fratton Park arrival is not one of them.
Certainly, there’s a formidable link between the combative midfielder's first-team presence and positive Blues results.
Naylor has missed three League One matches since his June 2018 recruitment from Burton.
In such absences, Kenny Jackett’s side have collected three draws, all occurring last term, among them the infamous February 3-3 scoreline at Southend.
The 28-year-old is a pivotal figure, his crucial presence emphatically recognised through earning the players’ player of the season accolade from his peers.
During the 2018-19 campaign, Jackett’s squad lacked genuine cover for a midfield spoiler who magnificently anchors the side from one of the holding roles.
No player came close to emulating Naylor’s strengths in terms of work-rate, mobility and physicality – plus leadership.
That obvious squad flaw persuaded Jackett to recruit Ross McCrorie on a season-long loan from Rangers.
Similar tenacious approaches towards enforcing the midfield area renders them unlikely to complement each other in this current first-team set-up under the Blues boss.
Nonetheless, McCrorie can step in to fill the gulf when required – should he be fit, of course.
In the 24th minute of Monday night’s FA Cup progress at Harrogate Town, Naylor was forced to retreat with a hamstring injury.
Jackett played down its severity during his post-match address, albeit the full extent of the damage still not yet certain.
However, considering the normally phlegmatic Naylor's reaction, it instantly betrayed a concern which suggests this is no minor issue.
Regardless, he joins McCrorie on the sidelines with a hamstring injury.
The task is now promoting a stand-in to replicate the quality of a player with 73 games and five goals and, as of September, entrusted with the captaincy.
Anton Walkes was handed the remaining 66 minutes of Monday evening’s 2-1 success, occupying a role previously served largely with distinction on six occasions.
Perhaps Andy Cannon can deputise, although there appear concerns he is not defensively suited for a holding-midfield role in Jackett’s 4-2-3-1.
The overwhelming truth is, however, Naylor cannot be replaced in this Pompey side.