It is first against second on Saturday as Pompey make the trip to London Road to face table-topping Peterborough.
The sides – like Barnsley, Sunderland and Walsall – remain unbeaten after seven games of the League One campaign.
But it is the Posh currently at the summit, having won six of their fixtures compared to five for the Blues.
The only points dropped by Steve Evans’ men so far this term came in a 1-1 home stalemate with Doncaster at the start of the month.
There have been convincing 4-1 and 5-1 victories at Rochdale and Plymouth respectively, although a late Ivan Toney strike was required to see off Southend last Saturday.
Like Pompey, United finished just outside the play-offs last term and were beaten 2-0 at Fratton Park on the final day.
Evans – who was appointed boss back in February – ripped up his squad over the summer and brought in 18 new players.
Now the Blues will be looking for a better outcome than last season, when Conor Chaplin’s strike proved a mere consolation in a 2-1 defeat.
Pompey will still be without the injured defensive duo of Anton Walkes (groin) and Jack Whatmough (hamstring).
Dion Donohue misses out with a tight hamstring, while Andre Green is also sidelined by a knee problem.
Peterborough have no fitness concerns, with midfielder Callum Cooke available again following an ankle injury.
HEAD TO HEAD
Pompey: 9 wins
Peterborough: 7 wins
At London Road
Pompey: 3 wins
Peterborough: 2 wins
Seats will remain on sale until 4pm on Friday, but cannot be bought at Peterborough on the day of the game. Click here for more details.
Overseas subscribers and match pass holders can watch the action – now with on-screen graphics – and commentary will begin from around 10 minutes before kick-off.
Peterborough are the 6/4 favourites with Sky Bet to secure all three points, while the visitors can be backed at 17/10.
Click here to read our full betting guide and visit www.skybet.com/pompey to earn money for the club when you place a bet. Please gamble responsibly.
ALSO IN LEAGUE ONE
AFC Wimbledon v Scunthorpe
Bradford v Charlton
Burton v Sunderland
Coventry v Barnsley
Fleetwood v Accrington
Luton v Bristol Rovers
Plymouth v Blackpool
Rochdale v Gillingham
Shrewsbury v Southend
Walsall v Doncaster
Wycombe v Oxford