The Dees have struggled in their return to the top flight this season and are nine points behind second-bottom Ross County and without an SPL win in six matches.
The Northern Irishman, though, is not reading anything into Dundee's struggles.
"We are not stupid enough not to realise that if we don't put in a performance then we won't win," said Lomas. "It is a local derby, Dundee will bring a good support with them and they will be fighting for their lives so we have got to be careful about complacency. We will have to be at our best.
"One thing you can't guarantee in the SPL is three points, the league has shown that.
"Dundee were in a difficult position in the summer, not knowing if they were coming up to the SPL or not which was a nightmare for their manager.
"He has also been hampered by injuries which has affected team selection.
"But they still have good players like Colin Nish and Nicky Riley.
"However, we have to look after ourselves and make sure that complacency doesn't come in.
"We are at the end of a tough period of games over a short space of time and it will be down to who wants it most."
The former Manchester City and West Ham midfielder, pleased with the news that Aberdeen agreed to extend Peter Pawlett's loan deal by three weeks, is hoping to give the Saints fans a home win to enjoy before the winter break.
He said: "Our priority is to get the win at home before the break then the players can rest their legs for a week or so.
"As I have often said, I have been happy with our performances this season.
"The most glaring thing, though, over the last six to eight games is that we haven't been converting our chances.
"If we had nine or 10 points more on the board then I don't think anyone could grumble."