Gay was named on the England Lions tour to Australia last winter to get on the radar, and he has impressed with how he has started the county season.
His efforts included a match-winning 159 not out to beat Lancashire last month and other scores of 129 and 128.
And with established opener Zak Crawley struggling to make runs for Kent, Gay has taken his chance, and even though he has batted at three for his county, he is an opener by trade.
Gay has a strong work ethic towards practice and Campbell believes England supporters not familiar with his batting will like what they see with the ex-Northants player.
“What you are going to get is a traditional, stylish opening batter,” said the Australian.
“Everyone has different ways to look at their game nowadays. Some are quite brutal when they come to hitting fours and sixes.
“Whereas as a left-hander, when you watch Emilio bat, it won’t take long if he gets a couple of cover drives away, you’ll think this kid’s got something about him.
“He’s very stylish, elegant and hopefully he’ll get the job done.”