Sinclair flew back to England on Wednesday when he did not make the final 23, but rejoined the England squad after Danny Murphy was forced out with a foot injury.
And he was pleased with his effort when he came on as a substitute against Cameroon.
"It doesn't surprise me that I felt a lot more comfortable, and looked a lot more comfortable, where I played against Cameroon because that's where I play for West Ham week in and week out," he said.
"Joe Cole has now been playing on the right and he plays well there for West Ham.
"So it was a little unusual in that, when we played for England, I had played on the right and he was on the left.
"Now I've had the opportunity against Cameroon and I feel I've done alright, certainly a lot better than the previous game."
Sinclair added that he feels indebted to Eriksson for being allowed to return home, if only briefly, to see his pregnant wife.
"I appreciate that and I'm not going to let him down now," said Sinclair. "I hope I can play some part in the World Cup.
"That's what I'm out here for and if I am called upon I am sure I will contribute and not let no-one down.
"If Emile (Heskey) starts against Sweden, I'll be cheering him on but also chomping at the bit for an opportunity and I hope I have given the coach food for thought."