But Davies, who nurtured Priestland's talent at the Scarlets before switching to Gloucester earlier this month, insists the 25-year-old will have an illustrious international career.
"Rhys is a quality player and he will play for Wales for years to come," said Davies.
"But it goes with the turf unfortunately when you play 10 for Wales.
"I can remember Stephen Jones and Neil Jenkins in my time - fantastic players. But you always have periods when you get a lot of stick if you are a 10.
"Rhys is having that now - he is used to it. He's done it with the Scarlets and he came through a very rough patch there and he just kicked on.
"It's part of his learning experience. I could see that Rhys was reading the game very well [in Australia].
"He didn't always execute what he wanted to do. He is playing within a game plan as well - there are a number of factors."
Wales made a slow start in Australia and lost the first Test 27-19 in Brisbane but they came out firing in the rest of the series and came agonisingly close to securing a historic win - eventually losing 25-23 and 20-19.
But Davies, who was officially unveiled as Gloucester's new director of rugby on Monday, reckons there is plenty to be proud of and to build upon.
"The margins were very tight. All three games Wales could have won," added Davies.
"Their commitment was fantastic. The way they played for the vast majority of those games was great and they are getting there.
"I can remember in the mid-90s going to Australia and being thumped by 50 points, so there is no doubt that Wales is moving forward.
"It's also great to see Wales Under-20s doing so well in the Junior World Championship and coming third.
"So, you have to look at the positives and not the negatives in this and look historically where Wales have been over the last 30 years and where they are getting to now and there is a lot to be optimistic about.
"It's becoming less of a mental problem. Physically we are able to compete. Technically we are able to compete and mentally now we are getting stronger and stronger."