Nathan Thompson is looking to rediscover the form that helped take Pompey to the top of the table.
The defender has recovered from a couple of injuries in 2019 and believes he has yet to return to his best.
And with the Blues dropping out of the automatic places following a scintillating first half of the campaign, he knows they must improve.
A visit to the Bescot Stadium to face Walsall is next up this evening and Thompson believes the side still have to aim high.
He said: “Our form since Christmas has been a bit stop-start and of course that’s been frustrating for us.
“We had the high of getting to Wembley and then an excellent result against Bradford, so it was disappointing to lose at Charlton on Saturday.
"When you’ve had injuries it does take a little bit of time to regain your form and it’s up to me to dig in."
“But there are still 10 games left this season and we certainly haven’t given up – we need to make sure we give ourselves every chance.
“I haven’t been at my best personally in the past couple of matches and I’m my own biggest critic – I don’t need anyone else to tell me if I’ve had a bad game.
“When you’ve had injuries it does take a little bit of time to regain your form and it’s up to me to dig in.”
Thompson’s Pompey deal expires in the summer and he revealed why talks over a new one have been postponed.
The 28-year-old said: “It got blown out of proportion a bit, but I’ve been in a position before where contract discussions broke down when we were fighting for promotion.
“At the time I felt it played on my mind and affected my performance, so I’ve asked the gaffer if we can put it on hold.
“I want to work hard to get this team to where they deserve to be and then we can discuss things. I certainly wasn’t trying to be greedy.
“I’ve loved my time at Pompey and have fallen in love with this club. I just wanted to be free of contract talks so I can focus on my football for the rest of the season.”
Thompson is still waiting to undergo dental work after losing a tooth in a nasty clash with team-mate Matt Clarke recently.
He said: “I’m not too bad. It’s a longer process than I would like and there’s a bit of work that I still need to have done.
“It’s about waiting for things to settle down in terms of the swelling, then the brace comes off and we take it from there.
“The ball just went up and Clarkey and I both wanted to win it. You can’t see what’s around you and unfortunately we collided.
“I could feel that one of the teeth wasn’t there and it was perhaps a bit more severe than we first thought.”