"I thought Thistle put us under a lot of pressure second half and we stopped passing the ball," Sporting Life quotes McNamara as saying.
"I also think that we should have killed it off. Stuart [Armstrong]'s chance - that kills the game off and settles everybody down.
"I thought at times we were maybe a wee bit nervous and were a bit too deep, which made it hard for the forwards to go and press the ball, so it's something we need to work on in getting up the park."
Dundee are back in action next weekend when they face St Mirren in the Scottish Cup.