The Brentford midfielder was making his first appearance at the Parken since last year's cardiac arrest.
Vestergaard said: "He played with an ease, and things may have fallen a little. It may have really dawned on him how happy he is to play football, and then the pressure that has been on Christian for many years since he has been our best player may come a little second.
"I think Christian enjoys every moment. Football is not everything in life, but for us football players it takes up quite a lot, and for Christian and the rest of us who have experienced it up close, football is the most important of the not so important things.
"Christian looks like someone who just loves to be back, play football and play for Denmark. I think we perform best when we are well, and it looks like Christian is well."