Anton Walkes’ injury is proving more of a problem than what was first expected.
And Kenny Jackett must quickly find the correct midfield balance again if his side are to achieve a League One play-off spot.
The Spurs loanee will be sidelined again for Charlton’s visit to Fratton Park after picking up a hamstring injury at Rochdale.
He’s also expected to be out for next weekend’s trip to Bury.
And, in truth, his absence has disrupted the poise in the Blues’ engine room.
Blessed with versatility, Walkes operated at right-back in his first nine games following his loan arrival in January.
Yet it was at Walsall when the 21-year-old switched positions with Nathan Thompson.
The former Swindon captain moved back to the right-hand side of defence, with Walkes deployed in Pompey’s engine room.
Jackett’s thinking behind the reshuffle was shrewd and it paid dividends.
Walkes, more mobile than Thompson, was tasked with screening the Blues’ rearguard.
And, more importantly, his job was to nullify the threat of Saddlers talisman Erhun Oztumer.
And he did it immaculately.
The Turk, recently named in the PFA League One Team of the Year, offered little in attack, with Walkes neutralising his usual potency to engineer Walsall breakthroughs.
The former Atlanta United loanee retained the role for the 2-1 victory over leaders Wigan two days later.
And this time it was Premier League-linked Nick Powell whose game was affected.
With Walkes playing in the holding-midfield role, it allowed Gareth Evans and Ben Close to maraud forward and support the forwards more frequently.
Against the Saddlers, Evans put a high number of dangerous balls into the box before eventually scoring the winner.
Meanwhile, Close had a few opportunities at the Bescot Stadium and was brought down by Dan Burn to win Pompey a penalty against the Latics.
Yet since Walkes collected his hamstring problem, Jackett hasn’t quite had the same influence in central midfield.
Close has dropped into the hole and, in fairness, has adapted seamlessly..
Evans has continued to impress in a central role – but it’s who fills the final berth which Jackett has to decide upon.
Stuart O’Keefe was handed a start against Plymouth alongside Pompey’s vice-captain.
After a four-month injury absence, he was his usual energetic, tenacious self at Home Park.
However, Jackett felt at the start of the second period he needed a player who would press the Pilgrims defence higher up the pitch.As a result, O’Keefe was replaced by Connor Ronan on 58 minutes.
And the Wolves loanee had a big impact in the final 30 minutes, with the Blues pushing for a winner.
Ronan then replaced the Cardiff loanee in the starting XI at Bradford on Tuesday.
Jackett would have been hoping for more of the same from the Rochdale-born talent.
But Ronan didn’t get on the ball enough and failed to display the prowess and intelligence he’s so capable of.
With Walkes sidelined, Jackett no longer has the flexibility to move Thompson into his engine room.
The 4-1-4-1 formation is proving profitable for the Blues but since Walkes’ absence they’ve picked up one point from a possible six.
By Jackett’s own admission, Pompey need to win their three remaining games to grab a top-six spot.
Finding the right balance in central midfield could be key.