Pompey boss Kenny Jackett admitted Ross McCrorie was walking a tightrope against Blackpool.
The on-loan Rangers midfielder was substituted during Saturday's 1-1 draw because he was one foul away from receiving a second red card of the season.
McCrorie was booked in the first half at Bloomfield Road felling Sullay Kaikai.
The Scotland under-21 international committed numerous fouls in the second period and was told by referee Chris Sarginson he was on his last warning.
McCrorie was sent off in the Blues’ opening-day defeat at Shrewsbury.
And Jackett revealed the risk of McCrorie being cautioned again was why he was replaced by Anton Walkes on 76 minutes.
The manager said: ‘I thought Ross was maybe going to get sent off.
‘The referee said to him one more foul and that’s it.
‘But for Anton, he came on and did well – I was pleased with him.
In the final period, we came through it and had some chances.
‘Physicality, I felt Walkes coming on for Mcrorie, who was down to probably his last foul, and Ellis Harrison coming on gave us a little bit more power and helped us towards the end.’