Guy Whittingham insisted he was forced into the substitution of Simon Ferry shortly before Exeter gave Pompey the shock of their lives.
Appointed Blues skipper for the visit of the Grecians in place of Johnny Ertl, who had dropped to the bench to accommodate Thery Racon, the Scot had been a strong influence in the midfield.
Pompey were in control at 3-0 when he was withdrawn in the 72nd minute for Ertl – but three minutes later Danny Coles started the visitors’ fightback.
Substitute John O’Flynn netted nine minutes later to spark a nervy finale which consisted of six additional minutes – much to the agony of the Fratton faithful.
By the time of Ferry’s departure, Whittingham had already used Andy Barcham, who brilliantly created the third goal for Ryan Bird.
He would also bring on David Connolly for Patrick Agyemang with the scoreline at 3-1 – but is adamant he had no choice but to substitute his captain for the day.
The Pompey manager said: ‘Simon was just feeling his hamstring a little bit.
‘Nothing had gone, it was just tightening up, but we didn’t want to take any risks.
‘That was it, purely just because of that.
‘At 3-0 up you think you have a player on there who, if he plays any more minutes, might pull his hamstring – so you bring him off.
‘I was as nervous as any Pompey supporter at the end.
‘We had been in control but knew they had it in them to change shape and cause us problems.
‘It was just later in the game rather than earlier.
‘Trevor (Carson) let the ball slip through his hands for their first goal and he has apologised.
‘Then at 3-1 I would have done the same as a manager.
‘I would tell our players to get into their box, just get up there – you haven’t got to worry about conceding another goal because you are two down already, who knows what can happen.
‘That is what they did. They threw up the ball into the box and threw lots of players forward.
‘If you allow Exeter to pass, they are a good team.
‘They change their systems a lot and went 3-4-3 near the end and put us under a lot of pressure.
‘We won, though, and the run continues, which is great to see.
‘We keep saying to ourselves it’s that top seven which is our target and we will keep striving towards that.’
Pompey’s key performer was Bird, who netted twice, while Ricky Holmes also scored.
Bird had been given the nod ahead of John Marquis, who dropped out of the 18-man squad entirely and is now expected to end his loan spell.
But Whittingham felt the time was right to give the 25-year-old his first Football League start.
He added: ‘Ryan came on and scored a goal at Torquay and I know what a confidence lift that gives you – you suddenly think “I can score at this level as well”.
‘All through training last week he had been lively and bubbly, so I thought it was the right thing to do.
‘You know he’s got endless energy, he’s such a nice kid, so willing to learn and so willing to run out there.
‘He’s a good team player and took his goals fantastically well.
‘He is beginning to understand the game at this level a lot better as well.’