Two first-half goals and an early second half strike saw Celtic 3-0 up before Brogan Hay got one back for the Gers.
Vignal said although his side did grow into the game, they had too much work to do by that point.
He said: “It was a strong game, I am not naïve I know where we are right now.
“We are just starting the project so of course Celtic are a strong side physically, tactically and technically so we can only progress and improve.
“I said to the girls you need to start right from the start.
“We started the second half really well and we scored a goal but it was too late you have to start playing like that from the beginning.”
Vignal is expecting challenges each week as the new project develops.
He added: “Like I said to the girls I know where we are there are four months to go and it is a new project and I am not naïve.
“That’s what I said to the girls chin up be positive and we start again tomorrow.”