Rahul made 57 off 78 deliveries in his 136-run opening stand with century maker Rohit Sharma to put India on course for an 89-run win.
The paceman walked off the field without completing his third over after developing a niggle in his left hamstring.
India made it 7-0 in World Cups against Pakistan and it was all thanks to Rohit Sharma's match-winning and an all-round contribution from the bowlers.
Victory in this rain-curtailed clash saw India, who have now won all seven of their World Cup matches against Pakistan, remain unbeaten after four pool games at this year's edition.
It was one of those days when almost everything went right for Virat Kohli’s team after he lost what appeared to be a crucial toss.
He will take no further part in the game and Ravindra Jadeja took the field for the remainder of the Pakistan run chase.
India start as favourites in the round-robin match at Old Trafford, with two wins and a no result so far.
Babar holds the key for Pakistan against India on Sunday and the batsman has been fine-tuning his game by watching videos of Kohli.
India boast a 6-0 World Cup record against Pakistan and their supporters are willing to do whatever it takes to ensure that impressive streak remains unblemished.
Amir said his mother, Naseem Akhtar, who died in March this year, always prayed for his success.
While India are yet to lose a game at the World Cup, Pakistan have won just once so far in the tournament heading into Sunday's encounter.
It’s a matter of survival in the competition after having won just one of their four matches, with one washed out.
Amidst all the hoopla surrounding the clash in Manchester, Virat Kohli was in great mood during the practice session.
The organisers hire entertainers on match days to keep spectators happy. On Thursday, when there was no play for long hours, they were in demand.
The test for both teams would be getting back on the field unaffected after having spent nearly three days indoors.