"The quality was not where it should be and that emphasized the gulf and it is something we need to address very, very quickly," Miller said.
Celtic's biggest win at Glasgow rival Rangers in 120 years →
"We're absolutely delighted with the way we've played," Miller said. "A lot of the things that we worked on in the pre-season really came into fruition today."
Whitecaps beat Red Bulls 4-1 in opener →