The Warriors scrum-half delivered a sparkling try-scoring performance against South Africa after replacing Mike Blair almost two thirds into the 21-10 defeat by the Boks.
Now Cusiter, whose shoulder dislocation in September has thrust 23-year-old Pyrgos into the No.9 slot at Scotstoun this term, believes his fellow Warrior has given himself a great chance of a start against Tonga at Pittodrie in Saturday's final EMC Autumn Test.
The crocked Scotland international, who is on target for a December return for Glasgow, believes Andy Robinson's men can sign off with a win against the South Sea Islanders.
Cusiter said: "I thought that considering this was just Henry's second cap and that it was once again off the bench that he had a very good game.
"He injected real energy into our play and got us up and running again.
"He took his try exceptionally well and it was great to see a try like that, which has been worked and developed on the training pitch, being executed so well. "
He went on: "Henry has matured so much over the current season with Glasgow and he has shown that he has the mentality to cope with the big games – and they don't come much bigger than South Africa at Murrayfield.
"So I think the fact he has come on and made a real difference, not just in terms of taking his try but the way he lifted the tempo for Scotland, will give Henry a great chance of a start against Tonga on Saturday.
"That would really be a fantastic achievement for him."
Cusiter reckons that Scotland's hopes of beating the Boks for the second time in succession were dented by a lack of composure at key moments.
He said: "Considering how much possession we had in the second half it was disappointing that we did not take advantage of it. But I think at key moments there was a lack of composure.
"If you look at the line-out we had in their 22 at the two-thirds stage, we went long with the throw-in, but it was adjudged squint and we lost a great attacking platform at a key stage.
"If we had scored from that line-out then we would have given ourselves a great chance of going on and beating the Boks.
"So we were very much in it, but when it really mattered we just didn't play the odds as well as the Boks did.
"However, the platform is definitely there to finish the Autumn Series with a win over Tonga."
As a result of the consecutive defeats to New Zealand and South Africa the Scots have now dropped to 10th in the IRB rankings, which will almost certainly consign them to a position in the third tier of seeds when the draw for the Rugby World Cup 2015 is made next month.