Goals from Gary Roberts and Conor Chaplin sealed a 2-1 success for Pompey against Wycombe at Fratton Park.
The hard-fought win means Pompey are almost mathematically secure in the play-offs - barring a huge goal-difference swing.
Roberts struck in the first half, with Chaplin firing the second soon after coming off the bench before Wycombe pulled a goal back through Sido Jombati.
After a couple of early scares in the opening exchanges when Wycombe pushed forward, Pompey increasingly took command of the contest.
Kal Naismith failed to pick anyone out from a good position on the left, before Gareth Evans flashed a low shot wide of the near post.
After 23 minutes, Danny Hollands and Ben Davies both had low shots deflected straight to Wycombe keeper Ryan Allsop as the pressure increased on the visitors.
The lively Roberts missed a good chance on 28 minutes.
He took the ball inside two Wycombe players before lashing his shot high and wide of the far post.
It looked inevitable the goal would come with Wycombe quite open in defence.
And on 37 minutes the deadlock was broken with McNulty’s cross from the right giving Roberts an easy chance which he finished comfortably, sliding the ball high into the net.
Naismith then thumped a superb low shot against the post and it crashed back out before Wycombe cleared.
Enda Stevens then twice crossed low but nobody could get a touch before the break.
On 51 minutes Paul Jones made an excellent save, diving to his left to push a header from Gozie Ugwu behind for a corner, after a good cross from Sido Jombati.
Roberts sent the ball straight to the keeper after going clear following a mistake from Anthony Stewart.
Cook made a double change on 60 minutes with Chaplin and Freeman on for McNulty and Davies.
And it was Chaplin who quickly made his mark on 67 minutes.
He burst clear to reach a great through ball from Doyle and clipped the ball past the keeper into the far corner of the net.
Doyle was penalised for a foul on Bean and the visitors capitalised with Jombati netting the resulting free-kick.
His shot was curled high into the top corner over the wall on 74 minutes.
The goal sparked a spell of Wycombe pressure and Jason McCarthy’s shot was cleared off the line by Freeman.
At the other end, Chaplin’s forward flick sent Roberts clear but his strike was tipped over.
Wycombe substitute Garry Thompson tested Jones with a good strike from 20 yards and the resulting corner was scrambled away.
The final few minutes were nervous for Pompey, especially with five minutes of added time.
But Wycombe were unable to force another opening.
As the final whistle went Pompey had done enough for a vital 2-1 victory, taking them to the brink of at least the play-offs.