Babar struck 63 off 66 balls as Pakistan scored 348 in their 14-run win over England at Trent Bridge.
Flower has no doubts Pakistan's batting will continue to do well after they were knocked over for 105 in their World Cup opener against the West Indies.
"Babar has come a long way. His game is improving all the time,” said Flower.
"He's going to develop even more, close to being at the top of his game, he is really exciting and he is going to be one of the best players in the world."
Flower said Pakistan’s two contrasting performances were due to the element of ‘inconsistency and unpredictability’.
"I would say it's a bit of a both," said Flower.
"Yeah, we didn't adapt well to the conditions against West Indies. Technically, we were a bit poor on the day. And I think there were a lot of nerves being the first World Cup match definitely.
"Then the guys got over that against England and they showed their proper skills and it was a true test of character. They came through with flying colours in the second game."
But Flower has warned his players against complacency ahead of the game against Sri Lanka.
"You have always got to be respectful and they have got good bowlers. And, hopefully, the weather stays away, it is a bit poor, the forecast," he said, with Friday set for persistent rain throughout the day.