Kenny Jackett still views the battle to reach the Championship as an open race.
The Pompey boss, who saw his troops lose to Blackpool on Saturday, feels you can pick three of 10 sides to nail down one of the promotion slots.
Jackett’s side have been at the League One summit for over three months now, but there’s no complacency from their manager.
The 57-year-old is still wary of a number of challengers to his side’s position this term.
Jackett said: ‘It’s an exciting race and an open one still.
‘You could cap it at somewhere like eight to 10, and there might even be categories within that.
‘If you’re looking at the three promoted sides there’s still eight to 10 for it.
‘It would be a big run now for someone to break into that.’
Jackett pinpointed the likes of Charlton and Barnsley are teams capable of charging into automatic promotion contention, along with Doncaster.
The quality of all the sides in the top half of the table have the respect of the Pompey boss, while sides in the lower reaches can offer threat on their day.
Jackett added: ‘It’s the whole of the top half of the division.
‘I’ve always said the top half in League One is a very good standard.
‘The sides in the latter regions have runs when their best team is out, but maybe haven’t quite got the depth when the injuries come.
‘The top part of the league is very good all the way down.
‘They (Charlton and Barnsley) are good clubs and good teams. There’s Doncaster who are exactly the same.
‘Doncaster and Peterborough were sixth and seventh going into the weekend.
‘Then you are on to the likes of Blackpool and we’ve all been waiting for an Oxford to come through.
‘It’s a very good division and it’s one we have to be humble enough to know we have to compete very hard in to be successful.’