Oldham's victory over Yeovil on Tuesday night sealed Pompey's fate, although the prospect of a 10-point deduction when they exit administration means League Two football next term has been a reality for some time.
The 2008 FA Cup winners have now dropped down in three of the past four seasons but are on the verge of a takeover by the Pompey Supporters' Trust following a drawn-out tussle with former owners Portpin and hope to leave administration on Friday.
"I'm glad to say we've come out the other side and everything is looking a lot more positive," caretaker boss Whittingham told BBC Radio Solent.
"It's been such a difficult time and the club unfortunately found itself where it was,
"We tried, we remained competitive but ultimately it wasn't enough. I do think we've given everything we can given the circumstances."
He added: "We will hopefully have our first home game on Saturday with everything sealed (the club out of administration) and with new owners, so we want to get off to a good start as far as that is concerned. Then we've got our last game of the season and everyone wants to win the last game of the season."