Pompey were handed the biggest reminder of League Two's quality on Saturday - thumped 4-1 by Oxford United at Fratton Park.
But perhaps the hardest pill to swallow for the Fratton Faithful wasn't just the defeat, but the manner in which Whittingham's men self-destructed.
Not Pompey's finest hour by any means, however, the panic stations should be left well-vacant for now, at least, with just 90 minutes of the season played.
As usual, with any football season, weeks of build-up, expectancy and hope surround not just the football club, but the city itself.
And, perhaps more so for the South Coast side this year, after the fans played their part in rescuing the club from death's door.
Before the match, Fratton End fans held coloured cards to display the message: 'Ours' - a timely reminder of just what the club had endured over the past six years.
And credit to those at the club who gave all to save its very existence, as without that effort, passion and belief, we wouldn't have an opening-day defeat to bemoan.
Anyway, back to the football.
Five fresh faces started the match for Pompey, with John Sullivan, Joe Devera, Sonny Bradley, Andy Barcham and Simon Ferry all handed first-team debuts.
The hosts started the brighter of the two sides, with winger Andy Barcham proving a source of trickery, pace and industry down the left flank.
New boy Simon Ferry, who turned down a number of League One options to join the club, also impressed in the opening exchanges - showing a good range of pass and plenty of creative flair.
His effort, coupled with the enigmatic strike partnership of Patrick Agyemang and David Connolly, provided the U's with plenty of questions to answer inside the opening 30 minutes.
And it was Agyemang to get Pompey's League Two adventure underway - heading in a thumping effort into the Milton End net - a finish which was greeted warmly by the 15,681-strong home support.
And nobody seemed to celebrate that goal more than club chairman Ian McInnes, who leapt from his South Stand seat to applaud the goal, and rally support from all fans in his vicinity.
However, the cracks started to show soon after the hosts carved their way into the lead - some sloppy defending by the Blues' back-four allowing Deane Smalley plenty of time to pick his spot - lashing his equaliser past new 'keeper John Sullivan.
Pantomime villain Dave Kitson received a more-than-warm reception from the home support - the player who asked to be subbed off while playing for Sheffield United at Fratton Park last term.
However, a fresh-faced Kitson met Pompey yesterday; a striker with something to prove to those jeering his every touch of the ball.
An important role he played, too, showing excellent work in both boxes for Oxford - something we hardly saw either of during his Blues career.
And it was soon to be two for Oxford, as former-Havant and Waterlooville striker Alfie Potter showed the magic touch to drill his tidy effort into the bottom left-hand corner.
Two goals in five minutes for the visitors saw not only saw heads drop among the hosts, but Fratton Park also uncharacteristically silenced.
Half time came as a welcome break for Pompey - who had five debutants starting the match - offering a chance for Whittingham, Steve Allen and Alan McLouglin to air their rally-cries to their beleaguered squad.
But despite the interval, and a chance to regroup, any chance of a revival was soon halted.
Blues' captain Johnny Ertl was branded a straight-red for an elbow to Oxford midfielder Danny Rose - the midfielder using his arms as leverage in the air, however adjudged to have been reckless in his play.
And as the stricken U's man hit the deck, a sea of yellow surrounded the referee in protest - sparking a 22-man melee on the half way line.
Tom Craddock, who scored ten goals for Oxford last season, was joined by Romain Padovani and Ricky Holmes as second-half substitutes, however the trio could do nothing to stop the rot.
Down to ten men, and trailing 2-1, it was more than an uphill task for Pompey - who allowed the occasion to get the better of them during large portions of the match.
Throw in some reckless defending from Dan Butler and his back-line teammates, and it was game over; another goal each for Smalley and Potter condemning the hosts to an opening-day defeat.
Potter, who played and scored for the Hawks against Liverpool during the memorable cup defeat at Anfield, picked open Whittingham's defence on regular occasion and showed just why he's highly regarded at the Kassam Stadium.
And late into the game, as Kitson was substituted and given a standing ovation by the 2,500 travelling supporters, the 33-year-old striker made some ill-mannered gestures to the Pompey fans situated in the South Stand - an area largely occupied by families with small children.
As the full-time whistle bellowed around Fratton Park, those left in the ground were handed the reality check that was perhaps needed by some quarters - a reminder that even in League Two, you've got to carve your own success.
Despite the 4-1 defeat, though, there are some positives to take from the match - few, as they may be.
For many of the players donning the royal blue today, they aren't used to big crowds, with big dreams and even bigger expectations - a real learning curve for them.
And also, the effective play from Simon Ferry, who was highly-regarded by Swindon Town fans during his spell at the club, showed a new dimension to Pompey's midfield - raw creativity that we had not seen in pre-season.
And finally, the effort of Connolly - something we saw time and time again last season, was evident in this match. If you could bottle his determination, it would be a top-shelf brand.
Unfortunate as Ertl's dismissal, and subsequent three-match ban may be, it offers real chance for Holmes, Padovani and East to prove to the manager - and the fans - just why they deserve to be playing at this football club.
One game down, 45 left to go. Keep calm and carry on.
Dan Brett is the Pompey Live co-commentator, touch-line reporter and a freelance print journalist