Tal Ben Haim will be the first casualty of Michael Appleton’s Pompey vision.
The Israel international lasted just 45 first-half minutes before being hauled off at the interval at Vicarage Road last Saturday.
Now his time on the sidelines is set to be extended.
New loan arrival Joe Mattock will be granted an instant debut at left-back against Leicester tomorrow, ending Ben Haim’s ever-present league appearance record this season.
For Blues boss Appleton, the policy of employing a right-footed defender in the left-back berth needed addressing urgently.
It was a weakness he felt was ruthlessly exploited by Watford in the first half of last weekend’s abject 2-0 defeat.
That prompted yesterday’s recruitment of England under-19 international Mattock from West Brom on an emergency loan deal until January 2.
In fairness, Ben Haim has been one Pompey’s most consistent performers over the first 17 matches.
But Appleton is adamant changes have to be made post-Watford – starting with the left-back position.
Appleton said: ‘First and foremost, it would be nice to see a left-footed player playing down that left-hand side.
‘I think that is something I needed to address.
‘I just didn’t think the balance and shape in terms of the back four was right against Watford.
‘It looked as if we could be attacked consistently down our left-hand side.
‘After 10 minutes of the game you could see they were highlighting that.
‘I just felt I needed to make a couple of changes at half-time in terms of how we approached it.
‘At the end of the day, you have got to identify what your strengths and weaknesses are at times.
‘You don’t have to be a rocket scientist to see that on Saturday, after 10 minutes, they were clued on to it and looking to attack us quite a bit on their right-hand side.
‘There was a lot of space that we needed to defend and we didn’t defend it well enough.
‘I am not just talking about the back four, I think the whole team in the way we went about it.
‘There weren’t enough players taking responsibility to do their jobs and roles expected of them.
‘Hopefully, bringing Joe (Mattock) in and George (Thorne) in will improve the balance and the shape of the team.
‘Joe can go left midfield but he has probably been playing 90 per cent of his career as a left-back, so most of the time you will find him playing there.’
Such is Ben Haim’s versatility, he remains an important defensive option for the Blues.
He played the first two matches of the campaign at right-back, having served there during the entire pre-season.
Ben Haim made his name in the Premier League as a central defender with Bolton.
His displacement at left-back against Leicester tomorrow will inevitably put pressure on other defensive rivals to perform.
Now the challenge is on for Ben Haim to force his way back.
Appleton added: ‘That’s why you have a squad.
‘You get to pick only 11 of them, and if you are not in the 11 it’s up to you to get yourself back into the team.
‘Whether Tal plays at the weekend or whether he is on the bench, or whether he is in the squad, ultimately, they all get paid very well to be professional.
‘They must show good attitude in training every single day and the best XI will start for that particular game.
‘The other five will be on the bench, and if you are not on the bench, it is up to you to get yourself on the bench.
‘If you are not in the starting XI, it is up to you to get yourself into the team.
‘That’s how it works.’