The Deans head to the Royals tomorrow night in the Wessex League Premier Division (7.45pm).
Birmingham believes his men will come up against a Portchester side hurting from their FA Vase exit at Moneyfields on Saturday.
In fact, the Horndean boss reckons there could not be a worse time to come up against Dave Carter's troops.
But Birmingham insists performing to the levels his players did in the weekend FA Vase penalties loss to Brockenhurst will give his squad a chance of coming away with something at the OnSite Group Stadium.
The Deans boss said: 'They’re going to be a wounded beast - they’ve just got beat 2-0 in a local derby - so it’s not exactly a great time to play them. But we’ve still got to play them.
‘It’s about what we do now and I’m going to be looking for more of the same of how we played on Saturday (against Brockenhurst) because we were excellent at times with 11 men and 10 men.
‘I’m going to have to freshen up a little bit, the players put in a lot of effort on Saturday so there are a couple of changes I’m going to look at.'
Horndean have already lost at Portchester this season - suffering a 4-2 FA Cup defeat last month, Kieran Roberts taking full advantage of some poor defending to collect a first half hat-trick.
But Birmingham is hoping his men can show they've learnt their lessons from that defeat.
He added: 'I’m not being funny, there’s no point trying to say avenge that (FA Cup defeat), that’s done and dusted and in the past.
‘We have to learn from what we didn’t do the last time we played them and take it from there. Hopefully, fingers crossed, we don’t make the same mistakes again.'
Defender Jack Lee will be available for Horndean despite his dismissal in the FA Vase defeat to Brockenhurst.
Ben Anderson (knee) and Sam Hookey (hamstring) will be assessed ahead of the Royals meeting after picking up knocks against Brock.
Royals boss Dave Carter has Jake Raine available again after a four-match suspension.
Installed as one of the pre-season title favourites, Portchester have won just two of their six league games so far.
Both have been on their travels, at Bournemouth and Alton, and Carter - who has called Horndean’s visit a ‘massive’ fixture - knows his men need to kickstart their Premier Division promotion challenge.
If they lose tomorrow, they will be 10 points adrift of Horndean with a game in hand. They could also be trailing Fareham by 11 points (with three games in hand) and Baffins by 14 points (with two games in hand) by Wednesday evening if the Reds and Rovers win their midweek home matches.
The last time Portchester met Horndean in a league game was in February 2020 when Jason Parish (2) and Steve Ramsey netted in a 3-0 win at Five Heads Park. The hosts ended with nine man after second half reds for Ash Howes and Fuzz Kanjanda.