The Black Cats picked up a 1-0 success over Danny Cowley’s side to end a run of three games without a win.
Pompey forced the home side back in the first half but created little in clearcut chances, before losing their way after falling behind
The visitors threatened again after Michael Jacobs’ late introduction, but still look a side who don’t possess nearly enough to worry opponents in the final third.
Johnson acknowledged his side were forced to work for the win, but also highlighted his keeper wasn’t really extended.
He told the Sunderland Echo: ‘It was a very hard-earned win.
‘You can see the pitch is not really conducive to playing tika-taka football, and that’s the reasoning for bringing in the likes of Danny Batth.
‘I thought we were extremely solid today. If you look at how many saves Hoff has had to make, I can’t remember one of note, and we’ve had two or three really good chances.
‘It definitely wasn’t a classic, but it was well fought. After the first 25 minutes, when I thought they were the better side, a Corry Evans tackle got us going and we pressed and hustled better. We had two or three chances where we caught them on the ball.
‘The second half becomes a balance between trying to attack and wanting to be solid.
‘Look at how many players we've got out from the team today.
‘So we need to win all types of games and it's something that I recognised early in the season and that I don't think we addressed early enough, and the signing of Danny certainly does that, giving us that dominant first-ball winner.’
Sunderland continue to be linked with former Pompey striker Defoe, along with a host of sides including Oxford United, Charlton and Ipswich.
Reports emerged this week Johnson harbored concerns about bringing in the 39-year-old, after his Rangers exit - but the former Bristol City distanced himself from that talk.
He said: ‘It’s misinformation.
‘We’re working very hard to bring Jermain in and we’ve had good conversations [to that effect].
‘It’s an option.
‘It’s got to be right, both for us and for the player, I do think that, but don’t confuse us being thorough for not having interest.
‘I’ve got a load of respect for the man himself and what he could bring to the football club, simple as that.
‘We want to bring someone in of that ilk.’
A message from the Editor, Mark Waldron
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