John Mousinho is facing Colby Bishop concern at Portsmouth | OneFootball

Pompey's main goalscoring source has endured a frustrating start to the season

It has been an extremely respectable start to the Championship season for Portsmouth and John Mousinho, as they find themselves in eighth place after the opening five encounters.

After preserving their second-tier status last term despite extreme budget constraints in comparison to their 23 divisional rivals as well as a well-documented injury crisis, progression has been the buzzword at Fratton Park across pre-season and the early weeks of the current campaign.

Mousinho's side have certainly shown signs of said progress compared to this time last year, albeit the fixture computer has been way more generous than it was on their initial return to the Championship.

Yet, despite remaining as competitive and defensively solid as ever under the former centre-back, it will be a slight concern for the Pompey boss that his side are yet to start fully firing in front of goal - a theme which was evident in Sunday lunchtime's goalless draw at St Mary's against Southampton, in what was the first league meeting between the South Coast rivals since April 2012.

Although the Blues have welcomed an array of new creative and attacking options to their ranks, as well as retaining the services of Josh Murphy amid late transfer window interest from Leicester City, a lot of their goalscoring output hinges on the normally-reliable Colby Bishop.

However, the club's early-season inefficiencies in front of goal has been summed up by some ever-so slightly alarming statistics involving the 28-year-old.

Colby Bishop has been a key asset for Portsmouth during John Mousinho's tenure

Arguably, no one has been as important to Portsmouth's progression from an on-pitch perspective during Mousinho's two-and-a-half years in the dugout than Bishop.

In his first season with the club - during which the current boss was appointed midway through - the man who joined from Accrington Stanley for a reported £500,000 netted 20 times and posted a further four assists, before going one better in terms of strikes the following season as Pompey returned to the Championship for the first time in 12 years.

Unsurprisingly, there was plenty of anticipation surrounding the centre-forward's potential exploits in the second-tier for the first time in his career. Bishop certainly proved his worth once more, returning from a heart scare to find the back of the net 11 times in just 32 league appearances, with Portsmouth being the third-highest scorers in last season's bottom half through an overall tally of 58 as they survived by five points.

John Mousinho will hope Colby Bishop can rectify early-season goalscoring concerns for Portsmouth

As previously mentioned, the services of Bishop and Murphy - who also posted the division's joint-highest assist total last season with 14 - give Portsmouth a chance of edging any narrow contest across the 46-game season.

So far, both of the side's league victories have come by a one-goal margin against Oxford United and Preston North End, whilst the striker's solitary goal thus far came through a powerful header in a 1-1 draw at West Bromwich Albion on August 23rd.

Even in Sunday's local derby, Bishop once again led the line well for Mousinho's side, pressing from the front and getting himself into prime goalscoring areas. However, he is clearly lacking the clinical touch at present, only scoring once from an xG of 2.71 and missing four big chances - the highest tally out of any Championship player so far this season.

Despite featuring in every game so far this season, it hadn't exactly been a smooth sailing pre-season for the forward, who was a doubt for the season opener against Oxford after sustaining a groin issue, perhaps hinting as to why Bishop has been unable to reach his maximum level as of yet.

However, with there still being 41 games to go, those at Fratton Park will continue to have full confidence in their main striker to eventually click into gear and reach a double-figure tally for the fourth consecutive season.