While the former All Black has been sidelined with a foot injury, Stephen Myler has taken his chance to shine with some outstanding performances at fly-half.
Spencer was fit for last weekend's defeat at Saracens, but he had to make do with a spot among the replacements and Mallinder isn't guaranteeing that the Kiwi will get a starting berth this weekend either.
Asked if Spencer will start against Scarlets, Mallinder said: "It is a good question and one quite a few people will be asking
"I'm delighted with how Stephen Myler has done, I'm pleased Carlos is now back to full fitness, he played well in the 15 or so minutes he came on against Saracens, so we have got lots of options there.
"It is something we will have a look at this week."
Mallinder will also spend this week analyising the performances of some of the fringe players given their chance to shine at Vicarage Road.
Players such as Matt Lord, Barry Stewart,
Paul Shields, Nils Mordt and Chris Mayor were all given starts in the 33-19 defeat, and asked if they had taken their big chance, Mallinder said: "I think some did, I don't think everybody did.
"Some players actually played well. Saracens
did a similar thing to
us, they didn't play
what they would consider a full-strength side, but they still had a number of good experienced players in there.
"It was a disappointing day, we can't hide from that.
"We didn't play well, but we are not going to let that affect our season.
"Confidence in the group is still high, we will have a day off and come back and hopefully be even more together and looking to perform better against Llanelli."
Tickets are still available for Saturday's game against the Scarlets, which is being shown live on BBC1.
Tickets are £22 for adults and £13 for concessions and juniors. Call Northampton 581000 or order online 24 hours a day through the Saints website at www.northamptonsaints.co.uk