Both teams will be looking to bounce back from defeats when they meet on Saturday at Fratton Park.
But manager McLaren has made it clear to his QPR players they will really need to up their game or face joining Norwich in becoming a Championship side to fall to the League One leaders in the competition this season.
He told London Football News: ‘If we perform like we did (against Preston) against Portsmouth it will be a struggle.
‘You always get bad days at the office and that was a bad day at the office.
‘That wasn’t like us. It’s the first time in a long while I’ve been disappointed with the performance.
‘It’s happened before and will probably happen again but the best thing you can do is come in on Monday morning and get the work done on the training field.’
Pompey lost to Oxford and Kenny Jackett will be looking for a reaction from his players as well.