For the third away league game running, Pompey threw away a 2-1 lead to draw 2-2 but this one was the hardest to take after Jermaine McGlashan scored in the 92nd minute of the match.
It had all begun so well. Patrick Agyemang opened the scoring after just five minutes when he beat a stumbling Steve Elliott to the ball and slotted past goalkeeper Scott Brown.
The big man should have had a second after Jed Wallace and Yassin Moutaouakil combined to tee him up from close range, only for him to blast the ball over the stand, let alone the goal.
Cheltenham were being dominated in the first quarter of the game and Pompey really should have made more of some good build up play, but there was a lack of cutting edge up front and Whittingham's men were made to pay for their profligacy soon after.
Terry Gornell produced a through ball for McGlashan and John Sullivan needlessly came off his line to try and collect a ball he was never going to get. The Cheltenham player had no problem rounding the keeper and slotting into an empty net despite the futile attempt from Danny East to clear the ball off the line.
The hosts started to play their way back into the game after that equaliser but were pegged back again right before half-time thanks to some excellent work from Wallace.
The youngster was somehow able to get to the byline and beat his player before sending a low cross through to Johnny Ertl who blasted the ball into the roof of the net to finally score his first ever goal for the club, with ridiculous dancing celebration to boot!
Another Pompey goal almost immediately followed that as Ricky Holmes had a shot cleared off the line after being played through by Agyemang who had been causing the Robins many problems during the game.
The second half began in the same manner as the first as Pompey again kept pressing the Cheltenham defence and continued to create chances.
A clever free kick routine early on ended with Andy Barcham's overhead kick flying over the bar but the best chance came soon after when Barcham's shot was parried by Brown and there were three players lined up to fire the rebound in, only for Wallace to tamely strike the ball into the goalkeeper's arms.
More chances were created with the wingers getting plenty of joy out of the generous Cheltenham full backs but the game swung in the home side's favour when Whittingham switched Agyemang, Holmes and Barcham with Bird, Padovani and the returning Cooper on 78 minutes.
That old familiar characteristic away from home then reared its ugly head again as Pompey began to sit back and defend deeper and deeper. Whenever a Pompey player had the ball they would frustratingly give it straight back to Cheltenham and have to endure more self-inflicted pressure.
That pressure finally told in the second minute of stoppage time due to a miscommunication at the back between East and Sullivan, which allowed McGlashan through to tap the ball into the net.
It might have been even worse as Gornell scored with virtually the final kick of the game but the Pompey fans who were kicking fences and seats in frustration soon started gesturing to the home support to "sit down, shut up!" as the linesman's flag denied Cheltenham what would have been the cruellest of all late winners.
In the end, Pompey had to settle for a draw when they really should have been celebrating a win but the inability to finish chances and shut the game down as well as some baffling tactical decisions meant the points were shared.
Agyemang was guilty of missing a sitter but how the chance in the second half wasn't taken when there were THREE players able to score beggars belief. Surely, if David Connolly had been playing then at least one of the many chances created today would have been taken.
The triple substitution also has to be called into question. Holmes hobbled off so he had to be replaced and there was also the case to take off Agyemang as he was knackered but it could be argued that a tired Agyemang is still more use than a fresh Ryan Bird who did nothing to enhance his reputation.
Why Barcham was taken off is also anyone's guess as he didn't seem to be that tired and was one of Pompey's biggest threats along with the other two players that were substituted.
The management and coaching staff really need to change the mentality of this team when changes are made because it seems like a natural process for the whole team to withdraw and drop deeper when holding a lead away from home.
Where were the outlets to take the ball into the corner and waste time? Where was the cool head in the centre of the pitch to calm things down when others were losing their heads and giving the ball away cheaply? Why do Pompey cease to attack late in games that they are winning and have dominated for long periods? It isn't good enough.
There were some positives to take from the game. Holmes looks like a very useful player and his performance today was his best in a Pompey shirt. Sonny Bradley was also outstanding once again and he must be frustrated that the rest of his colleagues at the back keep making mistakes.
It was also good to know that Pompey can score goals without Connolly and therefore will rarely go a game without scoring. Unfortunately until the defensive errors are cut out and the mentality of this team changes then it's difficult to know where Pompey's first win on the road will come and fans will keep getting what is now becoming that familar feeling walking away from League Two grounds this season.
Pompey Player Ratings
John Sullivan: 4 - Two costly errors in judgement.
Yassin Moutaouakil: 6 - Supported the attack well but gave the ball away constantly late on.
Sonny Bradley: 8 - Continues to stand out above the rest.
Joe Devera: 5 - Headed clearances need working on and his passing was rushed.
Danny East: 5 - Mistake led to second equaliser.
Jed Wallace: 6 - Good work for second goal but missed a sitter and passing was very inconsistent.
Johnny Ertl: 6 - Almost missed when he scored but still not quite the player he was last season.
Simon Ferry: 6 - Went about his business quietly.
Andy Barcham: 7 - Always threatening so why was he taken off?
Ricky Holmes: 8 - A huge thorn in Cheltenham's side and unlucky not to score.
Patrick Agyemang: 8 - Good goal and tireless performance.
Shaun Cooper (Barcham 78): N/A - Did he really need to come on?
Romain Padovani (Agyemang 78): N/A - Didn't seem to know where he was supposed to be playing.
Ryan Bird (Holmes 78): N/A - Looks out of his depth and can't hold the ball up.
Source: Fratton Faithful