That pain was confounded as he took in the latter stages of this antsy encounter from the stands after being dismissed from the dug-out by referee Stephen Finnie.
As Thistle trailed by a solitary goal, Jags midfielder Paul Paton received a straight red with just 15 minutes remaining. A should-to-shoulder tackle on him from Stevie May wasn't well received by the midfielder who then scythed down his opposite number.
In truth, the offence didn't seem to warrant a punishment greater than a booking. But it was May's theatrical reaction that drew anger from McNamara, who clearly felt that the Accies player did everything he could to get Paton dismissed.
Off went the Thistle player and up went McNamara to the stand.
By that stage, Thistle had become frantic as they tried to claw back a game they had failed to really get going in until the clock was ticking and they were behind.
If his side had been sparkling last weekend as they thumped Dunfermline, they were flat and unimaginative against Accies, a team who are fighting for their very lives at the wrong end of the table.
McNamara had been forced to gamble on the fitness of Graeme Smith, throwing the experienced keeper into the starting line-up after regular Scott Fox was injured last weekend.
Smith, who has been without a club since leaving Azerbaijan this summer and has signed a deal until January, was caught out at the opening goal.
Ali Crawford's corner caused him all manner of problems but although initial viewings suggested he fumbled the ball into his own net, referee Finnie later explained that the ball had already crossed the line by then.
He did recover to pull off one good save from substitute Andy Ryan as the game drew to a close. But getting him up to speed will be one of the priorities for Thistle this week.
The Jags showed far more bite in the second period but although they enjoyed more possession and were far more direct, they struggled to break down a resilient Accies team.
They piled on the pressure, winning corner after corner, but they could not find the back of the net, much to the frustration of McNamara.
A Dunfermline victory today would enable the Fifers to draw level once more with Thistle at the top.