Canada skipper Sinclair took her tally for her country to 139 after
She is now only 19 short of the highest-ever tally in women's football of 158 by
Herdman said: "That is the player Christine is. You can contain her for a period of time but when she is on song, she is on song.
"That is truly the mark of a great player in that some days they are unstoppable.
"It is good Christine is roaring through the tournament now. That will give her the confidence to keep moving on.
"She has scored in successive games now and you are starting to see it is a little bit more than just Christine.
"We have relied on her for too long."
A draw could take
But Herdman said: "The word 'could' or 'might' is the biggest curse in football and our approach will be to try and win the game."
Coach Mkhonzana Mkhonza admitted: "This stage is too big for us but it is a good experience and next time we take part, we will be better for the experience.
"We have played well in patches but have not been consistent enough. When we make mistakes, we get punished and, when opponents make mistakes, we do not punish them."
London 2012 has given women's football in the UK an 'unprecedented platform' on which to create a lasting legacy, according to the Football Association's head of national game Kelly Simmons.