McDermott left his assistant coaching role at Leeds Rhinos to move into the hotseat at the London club last month but it was at Bradford where he made his name as a player.
McNamara, who has now been in charge of the Bulls almost four months, said: "We are really looking forward to the trip and with Brian McDermott down there, it will add a little bit extra with his Bulls connections.
"They are always tough down there. The key is getting your preparation right and hopefully we have done that this week."
Quins were beaten 34-0 at Salford last time out but they have not yet given up hope of reaching the play-offs and McNamara sees plenty of dangerous players in their side, not least in former Bull Henry Paul.
"Mark McLinden is on fire and Henry Paul is now right back into rugby league and they have a very strong, solid, workmanlike side right throughout," McNamara said.
"They are very tough to break down and we will be expecting to play them at their best."
Bradford could also face a reunion with another of their former players in Quins full-back Paul Sykes, who has been out since March after suffering kidney damage.
Sykes said: "It?s been a long old journey but I?m really happy to be back with the lads.
"I didn?t really think I would get back on the pitch this season but I kept on hoping it might happen. I?ve been training with the team for a few weeks now and I feel good.
"I?m not sure if I?ll get a start but just to be named is brilliant."
The Bulls are hoping utility man Paul Johnson will be fit to play after two months out with an elbow injury.
Harlequins RL 18-man squad: Bradley-Qalilawa, Budworth, Dorn, Gafa, Haumono, Heckenberg, Hopkins, McCarthy-Scarsbrook, Mills, Noone, Paul, Purdham, Randall, Smith, Stewart, Sykes, Tookey, Williams.
Bradford Bulls 18-man squad: Hape, Deacon, Vagana, Gene, I Harris, McKenna, Newton, Lynch, Meyers, B Harris, Withers, Ferres, Vainikolo, Henderson, Langley, Pryce, St Hilaire, Bai.
Referee: B Thaler